Mega's were a horrible idea and I'm glad they're gone.
This. Most of the designs aren't appealing either, with the possible exception of Mega Charizard (which could have been made into a regional form) and Mega Diancie (which could have easily been a form change a la Hoopa Unbound).
- Pokemon should stop adding new mons after we hit a thousand. It's too much at this point to keep track of them all.
This too, although I have my reservations. New designs are part of the long-lasting appeal of the games, but I'd rather have about 40-50 new Pokémon that are well-designed than 80-100 that are mostly forgettable. Also, more regional forms! I don't think the concept has been fully tapped yet.
As for my own opinions...
-The Let's Go games were genuinely good, both as games on their own and as remakes. My only problem with them was the reduced Pokédex, but they were the most fun I'd had with a Pokémon game in a long time. Plus, they look fantastic, perhaps even better than Sw/Sh.
-HG/SS are great games but I sometimes feel they... missed the mark on some of the character redesigns. Case in point: Will and Karen actually looked like specialists of their preferred types in Gen II, but they don't in Gen IV. I also feel this happened in retrospect with Lance and
especially Koga's designs after LGPE came out; their designs in the latter games were so good, it's hard to look at their Gen IV designs in the same light again.
-HG/SS also botched Eusine's characterization by making him focus only on Suicune. They should have kept his general knowledge of the Johto legends as well as his continued presence in the post-game from Crystal. (In fact, I refused to catch Suicune in my last playthrough of SoulSilver because I didn't want him to disappear for good). If there's ever a Johto re-remake, I hope this is recitifed.
-As much as I love the original Kanto adventures, the next time we revisit the region (after a possible Johto re-remake) should take place farther along in the timeline - 5-7 years after G/S/C at a minimum. That said, the idea of revisiting Kanto and not finding any familiar faces in it does cause me a bit of anguish, so not far enough in the timeline for everyone to be dead (unless they appear as ghosts).