He was incredible in Life as a House. If anyone is in doubt as to Hayden's talent as an actor I would urge you to check that movie out. It was released a few months before Attack of the Clones and I was super impressed by his range. I recall thinking he was going to be a good choice to play Anakin. An actor can only do so much with such weak material though and despite the few years I was a Prequel apologist, even then I knew he wasn't great in those movies. Then again none of the performances aside from Ian McDiarmid's were all that stellar but his was the best because his character's motivation was clear from the beginning so there was a lot for him to go on.
It's interesting how Ewan's biggest gripe with the Prequels was his aversion to blue or green screen and the conceptual void he and his fellow castmates were stuck floundering in. As groundbreaking as those films were technologically, it's clear the actors needed more to go on. I've worked on some very small indie productions where the lack of budget and lack of sets and environments made a huge difference to the performance we got from actors. When we shot on location for some of the later projects we did, just having a real location made all the difference to the actors being able to get in that headspace enough to buy into the script. The series was sort of a Twilight Zone inspired webseries and we shot in black and white. Between that style of shooting and not being stuck in the limited spaces we had available to us previous, we were able to take advantage of the historic buildings to use their old New England atmosphere to build the tension the script needed.
Acting may be pretending but as an adult we lose that ability to imagine the same way we could when we were children and if everything aside from your costume is missing, having to fill that in with your mind and hit your marks, and remember your lines, all while staring at a blank wall of green, I can understand why their performances suffer. Even when Harrison Ford described working on Crystal Skull he made a comment about how when he walked onto one of the main sets inside the temple towards the end of the film and he was in awe of the detail. To see a veteran actor respond that way proves how the efforts of a production can really sell the actor on what they're doing.