Spells usually do use MP.

Abilities usually don't, and the game has become ability-centric, so you may have a point with that.

Weaponskills used to use TP. But TP was (in my experience) mostly irrelevant unless you did AoE for long periods of time, or received large buffs to Skill Speed, neither of which I noticed if I was in a good party that killed things fast, or without unusual circumstances, or using Sprint (which used up all your TP). In practice, TP was mostly annoying, at least until Stormblood with the abundance of TP-related role actions, but then it was just annoying the rare times it did become an issue.