Clunky as in things like enemy AI isn't great, equipment sometimes doesn't work until you fiddle with it (actually that's sort of unintentionally realistic), and sometimes quests are buggy, objectives aren't clear and sometimes don't trigger.

But it's a huge and very flexible open world (open galaxy really) game where you make your own goals much of the time. Some things are not going to be perfect but there is no other game like it if you enjoy the building, exploring, and freedom.