I used it because he says "No" in it lol. It's not his best scene but at least McDiarmid's performance is fun and entertaining, which you can't say for many of the others. I'm arguing it wasn't terrible, not that it was incredible.
I thought Liam was decent in TPM too. Definitely one of the brighter parts of the film.
This is my metric for acting performances: in a good movie, in a normal, typical, well made film, you don't notice bad acting or badly acted scenes. Mostly because they don't exist. In most good movies, the acting is good or good enough. That's just a basic standard for most good films.
Not one of the prequel films meet this standard. Across all 3 films there are multiple times each principal actor gives a terrible/bad/flat performance. That doesn't happen in good, well made, well acted, well edited movies. So when there are multiple poorly acted scenes for each actor in the cast, I can never say said actors were great or even good.
Liam Neeson gave a flat performance in TPM. He wasn't awful but he wasn't good. That being said he was better than everyone else in the prequels.