Thanos is very skilled. He doesn’t throw down because he likes to push himself. He prefers to out think his opponents. He lives for challenges, the more difficult to better. He prefers to out think opponents unless they are really strong then he fights them.
And he was nothing like Jubilee, Wolverines side kick and long term damsel in distress.
The fact is that hand to hand combat is more than throwing a punch and dodging a kick. There is a mental part of combat, tactics. And that is what makes Thanos so tough. He thinks 10 step head and looks at all the possibilities.