I think the Gen 1 games' myriad of glitches adds to the generation's unique appeal. The games themselves as they were intended to be played are obviously awesome in and of themselves, but the sheer volume of ways you could unravel them is something special, and is a part of Gen 1's appeal that sadly, no remake can ever recapture.
The elemental monkeys are cool and underrated for ingame use. The Pansear line in particular has only gotten better as of Gen 6 due to the Incinerate buff. And Simisear just looks cool.
Good Shiny colors > ugly Shiny colors >>>>> not being able to tell it's Shiny until it sparkles
It's OK to like either Plusle or Minun without automatically lumping the two together.
Let's Go Pikachu and Let's Go Eevee are good games.
PWT >>>> Battle Frontier
Z-Moves > Mega Evolution >>>>>>>>>>>>>>>>>>>>>>>>>> Dynamax
Phione's cute appearance validates its existence as a Pokémon, even in spite of being objectively inferior to Manaphy in terms of viability in every way conceivable.
Gen 1 Glitches: Honestly I agree. I feel like Pokemon Red is a ton more interesting to revisit compared to something like the original Super Mario Bros. You could even compare it to Super Mario 64.
Monkeys: I don't care about the Fire or Water monkeys but I actually like Pansage and Simisage. Nothing crazy, but it's not a bad design at all. Weird how monkeys are some of my favorite animals and yet the only ones I like are Simisage and Oranguru (maybe Primeape, he's funny)
Shinies: Hard disagree. Atleast with barely changed Shinies, it doesn't actively make the Pokemon worse. For a design like Garchomp and Gengar, I'm glad their shinies don't make them look awful, even if they're very boring and plain.
LGPE: These games definitely have stuff going for them but I couldn't get into it because of the catching mechanic.
Gimmicks: I'd have to say Z-Moves > Dynamax > Megas. This is mostly from a casual standpoint. I honestly like a lot about Z moves. I like the goofy dances, the powerful animations, the names, how they replace "badges" in USUM. They feel especially epic in the Anime. Dynamax is also cool too, I like how epic it makes battles feel in the game. Megas are fine, but I have a lot to pick with them. For one, it completely ruined the chances of Pokemon like Mawile, Bannete, and Sableye ever getting evolutions. That's fucking annoying. I also dislike how they were handled in game. In a standard X playthrough, you only get access to the Kanto starters Megas, Mega Ampharos (for some reason), Mega Lucario, Mega Gengar I think, and Mega Abomasnow. Everything else is locked behind post-game. While I like how they make weak Pokemon stronger, it also kinda feels...artificial? In a way. Like yeah now Mawile is good, but only in this temporary form. Competitive wise Megas quash the other two though.
Phionne: I'd agree if Manaphy wasn't way cuter than Phionne