At the risk of taking another credibility hit, I thought Reeves' performance in The Matrix was pretty good. I probably feel that way because I expected so little, but he made me forget I was watching Keanu, made me believe he was Neo, so I don't think he's as bad as some people make him out to be. He played that role reasonably understated.
He's very believable as a man lost. I think you nailed it, he's not awful he's just limited.
You don't ask a Defensive Tackle to play in open space too often and you treat Reeves with similar sentiment.