He has more than just an engine. His engine probably is his biggest trait but that doesn't mean he has nothing else. Yes, I agree he has to be careful when tackling but that's every defensive player.
I think maybe you've missed the whole point of signing him - Ugarte frees up Mainoo. A more creative Mainoo is a much better chance of stuff happening. It also gives Bruno more creative options, he could get into better positions easier to give a lovely lofty ball to the wings.
I've watched a lot of clips on him earlier today and one thing he's very good at is aggressive pressing, he gets right up in his opponents faces. And he does it at the heart of midfield where is a lovely place for another player to gladly intercept after major pressure was put on the opposition.
As per
FBREF, last season he out of 61.37 passes per 90, Ugarte has a passing accuracy of 91.2%. That's nothing to be laughed at.