These are all just my personal opinions, please don't take this as an attack if you really love A New Generation!

Sooooo... I'm going to flat out say it, I don't really enjoy G5 all that much :/ I really, really tried to get into it, but there's so many things that could be changed. I'm going to talk about it for a bit and tell you what I would change about the show first.

First, there are two major details I can't stand:

They have "sticky" hooves. They can hold things with their hooves but in a way that sort of defies the laws of gravity. Surely they'd be having a lot of trouble holding a cellphone or microphone with a single hoof. I get that My Little Pony is supposed to be similar to human society. We the viewers see that the ponies live in buildings, where clothes, have jobs, talents, etc. making them seem like ourselves: humans. I see nothing wrong with that, but we need to remember that they are still quadrupedal horses and need to retain some of those horse-like qualities. Letting them touch an object and have that object just cling onto their hoof seems so lazy to me. At least G4 took into consideration of how a horse might try to hold something.

The songs. Songs play a huge role in My Little Pony. Right off the bat, the intro theme song feels so... Gen Z? Like it's got this hip-hop beat going on. Personally, I don't really like it because I'm not huge into Pop music, especially today's Pop. There's nothing sweet or endearing about it. I get it, the creators are going for something fresh and new, something that young girls today would enjoy. But not every little girl is into the girly Pop music thing. I certainly wasn't that little girl! EVERY song is Pop-themed, as well. Like you HAVE to like girly Pop music or else this won't be for you. And I don't think that's fair.

Now let's talk about the general aspects of the show:

Setting:
The setting is set way too far into the future. The show talks about "Ancient Equestria," but normally, "ancient" would imply that at least a thousand years have past. Judging by G4's technology, I'd say it could be compared to the Western world's 1800's. In real life, it only took 200 years to get to where we are today (talking about real life here). 200 years ago isn't very ancient.
Maybe G5 could be so far into the future, that everything has a sort of cyberpunk feel to it. Or maybe magic in their world has dwindled so much, that creating technology was the only way to "replace" magic. Perhaps magic went away completely and the ponies no longer got their cutie marks and all that. There could be flying cars, spaceships, lasers, all the cool futuristic stuff. Then the ponies find all the "ancient" G4 things and discover they could have magic again, and there's a divide between wanting technology and magic. The creators could have gone so far with it, but didn't.

Plot:
The plot is so weak in this generation, I'm sorry ;0; As many viewers have pointed out, the fall of unity between the pony tribes always leads to complete destruction (Windigos). Well, we look at G5 and see that at first, the three pony tribes are divided and there's a lack of magic, yes, but other than that everything else seems pretty fine. The ponies in G5 survived fine without magic for so long, it almost seems as if... what's the problem, exactly? But this is a show for children, so I guess the creators didn't think it needed to be that deep, right? Uuuugh...
I have some ideas for a better plot, but I can't really focus on creating a solid one right now. Just SOMETHING different that makes more sense than what we were shown in the movie.

Characters:

So let's talk about Sunny Starscout first:
Her design doesn't really need to change much. Just add more color to her mane. I don't like that red, blue, yellow, primary thing going on. Instead, I think there should be a fuller rainbow effect. Also, get rid of that god-awful yellow eyeshadow.

Personality-wise? She doesn't really have a personality besides being the main character, rollerskating, and selling smoothies. In the movie she had more drive, but in the series, she's probably the least developed characters, and she's supposed to be the main one! Even her Alicorn form isn't all that grand. It just pops up every so often when it's needed.

She's Sunny Starscout, so I would say perhaps she could be a studier of the stars and planets and stuff. Maybe she uses the stars as answers for her problems? She should ditch the smoothie business and go for something bigger.

Next is Izzy Moonbow:

I wouldn't change anything about her design. I think it looks really nice the way it is. I think she'd look nice with golden eyes, but I saved that for a different character.

As for her personality, I like that she's into crafts and creativity, I just dislike how silly she has to be all the time. She can be eccentric, just give her a less stupid tone of voice. She almost seems as if she's drunk or high during the show. It just bugs me *shrug*

Also, I think her character could be tied a little more to her last name, Moonbow. Dunno how, exactly, I don't see how a pony could use a bow. Maybe with magic? Beats me...

Hitch Trailblazer:

So in the picture I gave him a buzzcut. I really shouldn't have done that, but I was more focused on his colors. I wouldn't change anything about him, except give him blue eyes to help give his character colors some contrast. Other than that, he's fine. Oh, and make his eyelashes less noticeable. YES, I know males have eyelashes, but personally, eyelashes to me mean feminine in character design. Not necessarily being a female, just have a softer, "girlier" appearance.

For his personality... I like that he can communicate with creatures, I see nothing wrong with that. I just wish he was a little more stern and serious, maybe a little more masculine, dare I say it.

Princess Pipp Petals:

Her original design is lovely and perfect, I hated trying to change it. My problem isn't with her design particularly, it's how her colors blend in too much with the others in the group. With Pipp in the group, I see so much orange and pink. I decided to make her the white one of the group and saw that the best option for her mane was light pink. I tried making blonde work, but it didn't compliment her accents very well. Her accessories are silver. I think silver fits because she is the younger of the two princesses, and silver is kind of the lower tier metal I guess.

AS FOR HER PERSONALITY OMG I CAN'T STAND HER, GUYS!!! She is so annoying and way too addicted to her cellphone. I think she sets a bad example for little girls. To me, looking up to Pipp is being told that it's okay to be addicted to social media 24/7. It's just not healthy!

I think Pipp's good side is that she has plans, BIG plans. I think her personality should focus on planning big events and staying close to her royal side. Also, please make her less "OMG YASS THIS IS AMAAAAAAZIIIING~!!!" and give her some damn dignity.

Princess Zipp Storm:

So this is probably the most dramatic change I made. Why did I make her so different? Well, I couldn't think of a good color that could say "storm". I tried green, but green is more naturey, unless her name had the word Derecho in it. So I went with an off black. It's neutral, and I don't think it clashes with the rest of the group. A blue body would look nice, but we don't want Rainbow Dash 2.0.

It's risky, as a very dark color might not appeal to little girls (says Hasbro). But I could see a good number of little girls thinking Zipp Storm is cool and badass this way with her mysterious, dark sky body, silver cloud mane, and golden lightning eyes and hooves.

I also got rid of her tooth paste mane. I can't stand her tooth paste mane :C It's so... tooth pastey.

And for her personality: Aaaarggh... for some reason she has to have detective skills and have all this spy technology. Ehhhh, it just doesn't work for me. She's Zipp STORM, so shouldn't she live up to that name instead? I can't think of a good example now, but I may have one later.

Freaking Sparky:

Sparky's original design, as MANY others have noted, just says Coco Melon, or whatever the hell it is. He's so uncanny, it's difficult to look at his weird human baby face and go "awwwwww, so cute!" I think he should be quadrupedal (like the other dragons in the show).

Now Sparky doesn't really have a personality at all besides "mischievous toddler." I think Sparky should at least be able to talk and communicate with the others. Maybe he arrived in Maretime Bay as a spy? I have no idea, but he just doesn't serve much purpose being an infant.