an unwieldy machine that require two people to operate it
means it is a big machine which needs 2 people work on it or fix it?
Yes, but “unwieldy” indicates that it’s hard to control, whether it’s big or small. In this case, the machine happens to be big.
A poorly made sword can be unwieldy. It’s not very large, but maybe it’s not well balanced, which would make it hard to control.
Sometimes we say that a very poorly written, verbose sentence is unwieldy.