As powerful as computers are they still have weaknesses. They don't have much idea about opening theory and there are many positions where you can leave them running statically for days and they still won't see ideas buried 15-20 moves deep. Also they often don't understand that certain endgames are not winnable (eg the opponent has a fortress, the opponent can simplify to tablebase draws etc).
A strong enough human should be able to work with the computer to perform better than the computer working alone. Whether I'm doing that or just sabotaging my playing partner's efforts, I couldn't say.![]()