Well I mean I'm not really sure why you're fussing about those mons of all things. This isn't Ambipom in RU we're talking about, let alone any sort of DPP OU Electivire. Sylveon and Conkeldurr are undoubtedly OU's worst Pokemon and I do want them to drop to UU, but only because they'd make wonderful new additions to UU. However, even they aren't half bad in OU and have okay niches, Clefable and Mega Gardevoir are usually superior options, yes, however, Sylveon still has some valuable traits, namely in that it doesn't occupy a Mega Slot like Mega Gardevoir does, and it also has the luxury of Dry Baton Passing on switch-ins to easily gain momentum. Conkeldurr also isn't half bad either. It's a decent tank, and even though it has issues with Fairies and is slow meaning it's easy to pressure, it's still a decent check to common threats in OU such as Tyranitar, Bisharp, and Mega Lopunny. Its Sheer Force set is also okay as it hits fairly hard with LO and has decent coverage to boot, making it a good hole puncher by allowing it to hit Gliscor hard with Ice Punch, or smack Fairies with Poison Jab, or something among those lines. Of course, neither Pokemon is that great as the former faces really stiff competition from Clef and Mega Gardevoir, and the latter is just really slow and has incredibly exploitable weaknesses, but they both have uses. They should probably drop to UU, but calling them "shitmons" is bringing it too far. They do have a couple of pretty valuable traits that keep them used.
And as for those UU mons. The only Pokemon in UU that is genuinely bad is Vaporeon, and that's because it barely has a niche in UU right now (to be frank, even Milotic is more useful than it). Other than Vaporeon and to an extent Milotic, the other mons that you listed aren't that bad, and they are actually very decent Pokemon in the UU metagame, just not quite as good as the UU staples. Those other four Pokemon mentioned are actually pretty decent Pokemon and have good niches in the metagame, none of them are even bad (why are people even still hating on Espeon, idgi). I mean sure, none of them are staples in this tier, but all of them have solid niches in the tier and are overall decent and effective Pokemon. Sure, they aren't by any means top tier threats in this meta, but none of them are even bad at all and have niches that some teams may want. They all have some pretty valuable aspects that give them reason to be used on some teams. I'm not sure why exactly you're ragging on them when they aren't even bad Pokemon and are nowhere near as bad as Scrafty or Trevenant when they were UU. Vaporeon is the only genuinely shitty one in that list tbh, and Milotic is somewhat questionable but it's an okay Pokemon on its own too despite being outclassed.
Basically, right now even the lesser viable Pokemon in OU and UU aren't half bad in the metagames and aren't by any means DPP OU Electivires or Ambipom in RU or something among those lines. The only shitty thing I can see is Vaporeon in UU but...ehhh....lol.