I've been binge watching a lot of "speed run X pokemon game with all pokemon" videos lately and one thing I've noticed is that in gen2, most of the TMs seem pretty universal - I feel like most pokemon in gen 2 learn about 75% of the tms and there's a lot of overlap in that 75%. Also, a lot of the TM's a just kinda, not super good? Most of the notable ones in Johto are either normal type moves, the elemental punches, or severely lacking in power or accuracy. And honestly, I really like that approach. I like the TMs being widely available moves that can be usable if you don't have much else (mud slap, swift, headbutt, even the elemental punches) but they don't overshadow a pokemon's level up movepool so there's still a lot of uniqueness. I think in modern pokemon games where you can get 150 TMs for the best moves by the 3rd gym and they're widely learned, a lot of uniqueness for each individual pokemon is lost
This is what I recall sucking a lot of the fun out of ORAS for me - how much more available high-powered TM moves were compared to RSE. Like, when you reach Mauville City, you're able to purchase Facade, Aerial Ace, Bulldoze, Charge Beam, and Dragon Tail - all moves which typically come much later in the game than this, and which all have very high base power and highly useful secondary effects considering the stage of the game you're at. Bulldoze for instance absolutely wrecks Wattson's gym.
Not just that, but the fact that TMs are infinite in this game makes choosing what should learn each move a non-issue. Sure, you might get a powerful TM early on in RSE occasionally - you get Steel Wing very early in the game, for instance. But you can only use it once, so you need to be careful who you use it on because they might not be suited to having it or you might choose to drop them from your team. In ORAS - mmm, Pelipper doesn't really suit having Steel Wing? All good, you can overwrite it without consequence.
You might think "but you don't have to use TMs" and yeah, obviously I don't. But the natural movesets of Pokemon are altered too, and pretty powerfully so. Whenever I replay RSE, what makes the early-game challenging (and enjoyable) is that a lot of Pokemon have fairly crap movesets early on and you have to work with that. Lombre, as a random example, is stuck with a bunch of low-base power moves well into its 40s, and doesn't even get a damaging Water move until level 49. Until you get Surf, your only options for STAB are the underwhelming Absorb or the unreliable Bullet Seed, which might not even OHKO a foe weak to them. This changes in ORAS as it gets Bubblebeam relatively quickly, and can one-shot a bunch of foes with it. Similarly, Combusken is pretty powerful but basically stuck with Peck (meh), Double Kick (good, but not great) and Ember (weak, but workable) until it evolves and learns Blaze Kick. Here, it gets Flame Charge early on which is a pretty gamebreaking move both in terms of its power and its secondary effect, and also learns Quick Attack significantly earlier than it did in RSE to add onto that. I just felt a much lesser degree of challenge in ORAS than I ever got playing RSE and I'm pretty sure little changes like this were a big part of why.