I did say "mid", not "bad." At least I bought and played through SS (albeit used at a deep discount a few months after release,) unlike some later games that I just skipped altogether. And they worked without crashes, glitches and framerate issues.
But to answer the question, and honestly, a lot of these are holdover flaws from G/S/C:
- The level curve is horrendous. Once you enter Kanto, there are some routes where the trainers have Lv50 Pokemon but the ones in the wild grass are still Lv3.
- Kanto itself is bare bones, pretty much the "We have Kanto at home" version of it. It is improved over GSC, but it still feels barren and boring.
- You can no longer delete Pokegear numbers. I actually had to restart my file because of this, and had to make a note of which trainers to avoid getting their numbers since their calls were so frequent and annoying.
- I found Mom's spending habits (if you let her save your money) a LOT more egregious than GSC. And some of the stuff she bought in the originals were unique like the dolls for your bedroom. In HG/SS it's mostly random-ass berries you can find on any route.
- I personally found the Pokemon following thing to be annoying, and found myself riding the bike a lot more often to circumvent it. It didn't help that it automatically chose the first Pokemon on your party list, and I have a habit of changing my team order quite often, which meant the follower changed just as frequently. Seriously, I haven't given the Bike that serious of a workout in any other game.
- Leaf does not appear anywhere in the game. They stuck with the same weak pushover that was in GSC.
- Rock Climb is required for some caves, which makes traversing them worse than GSC.
- Team Rocket without Giovanni is a sad, pathetic shell of its former self and rarely seemed like a threat.
- Kris > Lyra.
And honestly, the more modern graphics and remixed music took away most of the nostalgia factor that G/S/C had. As flawed as the originals were, I at least have fond memories of staying up late at night and exploring Johto after dark with them. I got no such feelings playing through HG/SS.
I
did catch a random shiny Meowth in SS, which I transferred to another game, so they weren't all bad lol
I mean, I'm completely baffled as to why BD/SP get so much hate. They weren't great games, but they were based on a good foundation (D/P). Yeah, the changes were few, but at least it wasn't a situation like HG/SS where many of the changes actually made them worse than the originals.
Then again, I have been known to have weird opinions, lol