Right, I can follow this argument in theory, but it simply doesn't match the experience of most players. It's widely agreed that the Souls games (+ Sekiro, Bloodborne, Elden Ring) are high difficulty, and that most encounters are not unfair.
The moveset is limited in terms of types of attack, but that's clearly not all there is to it. Difficulty comes from precise movement and timing. You can say the same for Hollow Knight, or Nioh, or quite a few others. In Devil May Cry, for instance, you've got a much larger pool of attack moves/combinations... but your timing and placement simply do not matter as much, which also means the requirement to know your enemy, recognise tells, & intuit upcoming moves is not as high. The result is that for a regular playthrough, Souls is harder than Devil May Cry, regardless of the size of your attacking moveset.