It's honestly pretty dull in BBS/DDD (and, now that it's available, in KH1FM HD).
It's fun in KH2FM though. You get enough bonuses in that game through equipment and Bonus Levels that you're still capable of dealing decent damage to bosses, but they pose an extreme risk to you. It's thrilling, not exhausting.
LV1 Critical runs in KH2FM aren't really that different, difficulty-wise, from something like playing a Devil May Cry game on the second hardest difficulty (albeit far less polished and tight, combat-wise). Your deaths are your own fault and you can get damn good at the game.
KH2FM, between guard, juggle, reflect, magnet, and dodge roll, gives you plenty of tools with which to defend yourself with i-frames and/or incapacitating your enemies, and you've got plenty of tools with which to deal damage too. It's also fundamentally a less strictly stat-dependent game than BBS/DDD are (look at the way that level-ups function in those games).