Something small that annoys me: Pokemon clearly designed for a thematic move to be used with them (not necessarily Signature) that they just simply don't want to use if played typically.
First example that comes to mind is Excadrill having Drill Run, yet learning Earthquake by level up as well (even EARLIER than it until Gen 8) which is a strictly Superior move in the all-single Main game where the level up moves are made for.
I might have given this case leniency before High Horsepower became a TR in Gen 8 and ALSO outclassed that as a ST option for Doubles. This differs from something like Ursaluna who has different use cases in theory for HHP vs Headlong Rush (Power vs Debuff trade off) or Mamoswine who only "naturally" learns Earthquake and HHP is a TM in any game with both moves for flavor (LA gives it since I think EQ is not there).
I feel this with Blaziken and Swampert in RSE. The former gets Blaze Kick upon evolving which is a really good move on its own merits, having a high critical-hit ratio but being significantly more powerful than most moves with a high critical-hit ratio like Slash or Poison Tail. The trouble is that Flamethrower is just generally a better option and that in RSE, of course, you get Overheat relatively early which is extremely powerful on Combusken if you've got one so Blaze Kick ends up feeling a bit redundant. It's a much better move on Pokemon for whom it's a coverage move they otherwise wouldn't get - Hitmonlee, Lucario, Mienshao et al. Emboar is in a similar boat, too - Heat Crash sounds nice in theory since Emboar is on the heavier side but in practice even Fire Punch is more consistent while Flare Blitz is by far the best Fire move Emboar can get, not least given that it gets Reckless.
For Swampert it's kind of tragic, because Muddy Water is exactly as powerful as Surf and has a potentially very useful secondary effect. The trouble is that, much like Overheat, you get Surf when your starter is likely to still be in its second stage and for an in-game run you obviously need Surf a lot so if you don't have another Pokemon to use it there's very little incentive to keep Muddy Water over Surf. Sceptile, alone, got a move unquestionably better than most other options - Giga Drain was significantly weaker in Gen III (and Leech Seed exists if you're desperate to drain HP), while Solarbeam has the drawback of a charging turn. Even Blastoise, which had Skull Bash as a (partial) signature move in the first two generations, had countless better options as far as Normal-type moves go.
In fairness it's why I think signature moves for later-gen starters have tended towards being status moves (Court Change, Spiky Shield, Mat Block), or those with a guaranteed additional effect (Mystical Fire, Spirit Shackle, Darkest Lariat, Torch Song, Aqua Step, Infernal Parade, Ceaseless Edge). Some even have more than one guaranteed additional effect, like Sparkling Aria, Snipe Shot, Flower Trick, and Triple Arrows - that just leaves Pyro Ball, which is mega powerful with very little drawback. They definitely seemed to realise how underwhelming starters' signature moves were and took steps to make them into moves worth using.
