How to express “too hard to use” in a word?

Question

I want to express that some tool is "too hard to use", which means its user experience is really bad.

I feel "too hard to use" is like emphasizing the difficulty of using it instead of the experience of using it, and the phrase is too long for me.

Is there any word or a shorter phrase that can express this idea?

Answer 1

unwieldy, Oxford Dictionary def: (of a system or bureaucracy) too big or badly organized to function efficiently.

or

cumbersome, Oxford Dictionary def: slow or complicated and therefore inefficient.

both come to mind. Both have roots in describing physical properties of an object but can be used for more abstract concepts.