I dislike how gen 4 simultaniously buffed many pokemon that couldn´t keep up anymore with an evolution, while also introducing lots of new pokemon that were completely outclassed and forgettable from the start. Did pokemon like mothim, kricketune, lumineon and cherrim really have to be that awful?
Not every pokemon has to have amazing stats of course, but I feel like a pokemon should at least be somewhat usable in-game. The power difference between like mothim and, say, Staraptor or roserade, is absolutely massive. It's odd to me that so many original gen 4 pokemon are so forgettable while Gamefreak did recognize some forgettable pokemon from the previous gens and gave them an evolution.
I'm actually, somehow and in some respects, of the opposite opinion. Recent generations have too few crapmons, if that makes sense. From Gen V onwards, and especially noticeable in Gen VI onwards, they tried to make sure that each Pokémon family had its gimmick or its competitive niche. Every Pokémon seems to be designed to perform some job or another in competitive play, to have its little trick to show the metagame and not be totally useless.
And that's fine, but it also effectively eliminated the potential for future makeovers. Be it through regular evolution, Mega Evolution, new abilities... there just isn't that much to build on when it comes to later-gen upgrades for recent-gen Pokémon. They already have their niche, their gimmick they were designed to play out, and stats balanced around that.
Take the loads of crapmons in Gen II, for instance. When they were new they were interesting, if not overwhelming. In Gen III, their shortcomings became more apparent, but they still had some of their novelty. And in Gen IV they were given badass makeovers to bring them up to speed with the rest of the metagame. 'mons such as Gligar, Sneasel, Togetic or Roselia would have been nothing without their Gen IV evolutions, and thanks to those evolutions the evolution families are cherished to this day, mainstays of many a playthrough. Mediocre Pokémon made great.
But now... it's like there's nothing old and outclassed left to bring into the limelight anymore. Notably, the Pokémon that got new forms and new evolutions in Gens VI-VII were mostly ones from Gens I-III. They're the ones with potential left to unleash. Weezing, Corsola, Farfetch'd, Linoone... they were easy candidates for an upgrade. But what forgettable 'mons are there from recent generations to give the same treatment? Ones that are mediocre and forgettable because they have terrible stats or lack a gimmick that defines them? You might make a case for Pyroar or Swirlix/Aromatisse, but even in those cases, their stats aren't exactly screaming "give me an evolution!" The evolution might then be all but cosmetic without changing much (in a vein similar to Rhydon -> Rhyperior), to avoid being overpowered - which would just make it pointless.
Worst thing is, all this is while more Pokémon than ever are created as single-stage or two-stage evolution families. There are so many evolution families that strictly speaking have room for more members, but it seems like the Pokémon were designed to be fully evolved and usable from the get go, making potential evolutions either overpowered or pointless. We still dream about evolutions for the likes of Chimecho, Qwilfish or Torkoal. There don't seem to be any Pokémon with that same potential in recent generations, and the signal this sends - "don't expect future cross-gen evolutions" is a little sad to me. It's as if a solid border was drawn along the edge of a dream.