CGI is great for things that aren't organic.
CGI is often, usually, terrible for things that are. And, right now, it's still terrible when it's the bulk of a set, but great when it's less than the bulk of a set.
Going back and watching something like The Thing makes me lament how much of that is lost. Or, really, anything with weight, like car chases and crashes. But then you have something like the world of Game of Thrones, which is often ridiculously well done CGI backdrops that are far better than old matte paintings (though I love the skill required to make those.)