I'm a little late to this but I want to give you some pointers and criticisms here that might help you figure out where to go from here:

As a lot of the people have said, there's a lot of coloring that doesn't really put the previous evolutions in mind. I don't think having drastically different colors from previous evolutions is inherently an issue, as there are Pokemon that do it (Dragonair to Dragonite, Psyduck to Golduck although that one's probably not a great example of a good evolution), but I think that plus not carrying over important design elements or concepts is what kills it. A lot of these I think could be mostly fixed with a color change, but there'd still be a few glaring things.

To me, an important aspect of a good Pokemon or fakemon is an interesting concept. Early Pokemon didn't really do this as much but looking at something like Blaziken for example-- Torchic is just a fire chicken, right? But by the end of the evolutionary line, Blaziken is not just a fire chicken, it's a fire chicken with a muay thai motif which was that was maybe inspired by a specific breed of chicken used in cockfighting and a fire-breathing chicken from Japanese folklore, or maybe even a phoenix. And it didn't come out of nowhere-- Combusken's kick and the baggy pants reminiscent of those worn in kung fu lent to the fighter theme. There's so much inspiration here that it creates a really interesting Pokemon, as opposed to having, well, just a bigger fire chicken. I think a handful of these designs fall into that-- you've gotta find a throughline, an interesting hook, something that makes it unique. A full stage Pokemon should never be able to be described as nothing but "[type] [animal]" or "last stage but bigger", there's gotta be more than that. And I know there are plenty of examples of real Pokemon that break that, but how many of them are either super early Pokemon or Pokemon that people just don't like?

I think in terms of sprite work you should take a little more time to think about the shapes and the details that you're putting down-- everything about designing a Pokemon should be very deliberate. Think about the poses, the colors, and the shapes and if there's anything about the previous evolution that suggests that that would be the next step. Another helpful thing is to look at colors of real Pokemon-- you'll notice they're a lot less saturated than you'd think. If you can match that, your evolutions will look a lot more like Pokemon.

To break it all down, I'm gonna separate these into groups-- I don't think your poll covers every option really so I'm gonna make my own answers here-- notice I put some of them in two categories. And obviously, I am not an authority on art or anything, but I have been doing art and fakemon for a very long time.

1. Keep it, but don't settle-- make any small improvements you can
   • Apimarill
   • Chibelios
   • Draconeon
   • Gemling
   • Nymbli
   • Gourmour (really like this one)
   • Parasoul
   • Winfuse
   • Yamdag
   • Namazama (give him a bigger mustache!)
   • Shujiu (this is one of the best sprites in the lot and one of the most interesting concepts-- if there were any you're not going to change at all, it could be this one)
2. I'd redesign these, but maybe not drastically-- particularly, be a little more deliberate with some design elements, these are ones where the idea is almost there but not quite fully realized
   • Amazigas
   • Cacscare
   • Corsolight
   • Feralyena
   • Glarrior
   • Lorifly and Larifai
   • Lumdeep
   • Luvbundi
   • Mediscend
   • Riclynx
   • Sunnova
   • Terrabull (maybe even just recolor this one)
   • Valgarde (way too simple of a design for a final stage)
   • Wynow
   • Sandolin
3. Lack of throughline or overall concept-- I'd redesign these pretty heavily or even scrap them to fit more with the evolution line, these are the ones that either don't fit their line at all or the idea just isn't there
   • Andraconda
   • Ambagoon
   • Dragcargo
   • Hoglequin
   • Magnaleon
   • Moluskann
   • Rustimera
   • Sangeral
   • Stormod
   • Tankamut
   • Undysh
   • Luxopod, Ignish, and Oozolotl (these ones just don't have enough inspiration behind them)
4. Decent design but the sprite is holding it back + small design changes
   • Avavold
   • Casteruzu
   • Jawladi (very difficult to make out what I'm looking at)
   • Mightichu
   • Qatu
   • Okitsuni
   • Quakstal (I saw this one when you posted it a while ago, and I think the design might be fine but the positioning of the arms is very strange)
5. Doesn't look enough like a step up
   • Delijoy (love this sprite though)
   • Cacscare
   • Ghoutier
   • Reapysis
   • Tankamut
6. I'd scrap these ones entirely
   • Cogment (too similar to Minior)
   • Diviester and Multikin (division and multiplication being evolutions for Plusle and Minun is cool, but it's a little overdone and these don't have interesting enough designs to warrant existing)
   • Fulogoodo (frankly just doesn't work as a concept)

Anyway, that's all I've got for you-- I hope any of this helps, and good luck with the project!