As a gamer, I find it rewarding when player skill and decisions make or break a battle. There is a feeling of achievement when it is an improvement in your own skill that leads to victory in a battle, not just the fact that your character is now of a higher level, or that your character is now equipped with more skills. I feel it is more rewarding that your own technique, methods and tactics have improved against a given enemy. However, it is also interesting and fun to be able try different things - using your own control. Turn-based is fun if the tactical element is great, but otherwise it gets boring and dry quickly - especially if your skill repetoire (like at the beginning of your game) is too limited, or if it is too varied, you have too many useless skills.
Having a smaller set of skills repeatable, but that both grow in power and vary in tactical value as time passes as well as more interesting movement styles and enemies. It's always interesting when a skilful player takes less time to grind than that of a new player, but knowing that the new player will catch up eventually in skill as well - and follow suit.
Having a system like this also introduces a new element. Because enemies will have to behave similar to players and behave in predictable patterns (unlike in an RPG), this opens up a new avenue, since enemy AI can have more flexibility and can create more of an interest in the enemy, compared to just knowing it's HP. This also means that I can have annoying enemies that die in one hit, but are difficulty to hit without a gun, for example, or enemies that are easy to hit, but difficult to take down.
Then of course, we have enemies that are unblockable, or attacks that not avoidable (but blockable or possible to resist against) in addition to more traditional buffs and debuffs that affect speed, damage, the ability to cast spells, and so on. All this test player skills considerably, and it wouldn't be an overstatement to say that a new player with a powerful character will be greatly mismatched and depending on how different the loadout is on the character - it is even possible that the new player will be unable to use the character at all!
(Of course, if it actually reached that stage, I'd say the game probably needs reworking on the ease of control.)