I know it's a bit unfair but it was basically my first thought lol
Which is sad since I read a few of the fluffier ones anyway.
I suggest you begin reading some more light-hearted ones, such as Majo to Houki to Kurobuchi Megane, Inugami-san to Nekoyama-san, Yuri Mekuru Hibi or Ayame to Amane.
Already read / reading them.
No of course there were a lot of abusable things in that gen as well but my main point is with how nondescriptive pretty much everything was it made the game extremely tricky to play and you could screw yourself over rather easily, especially due to most fights being not repeatable (meaning you could lose yourself out of money).
Maybe I'm just forgetting my times with the game before breaking it wide open, I guess?
That said, I'm not sure how these kinds of mechanics / missables matter to Persian's extra type coverage (through use of one-time TMs at that) not really being necessary :x Most people probably didn't even know about that and it's an irrelevant thing to most normal playthroughs. That's all my point was, really. I'd apply that across the board to every super awesome sweeper movesets that probably rarely got used for the main game (e.g., Tauros Body Slam / Hyper Beam / EQ / Blizzard, Starmie Surf / Psychic / Ice Beam / Thunderbolt, etc.). Awesome to utilize if you knew about it but not something that you needed to have done.