That has, historically been my issue with LGTM. It is ultimately a meaningless rubber stamp. Many people get a large PR and give it a quick scroll, type LGTM and move on. If I had it my way, every PR with over 100 LOC diff should require two PR code comments for a reviewer to approve it.
I see it more as “this result is commensurate with my experience,” the problem with it, of course, being reliant on the pilot’s experience. But otherwise we’re just talking about a “sniff test” on a number. LGTM sucks in software because software inherently is a lot more complex than a number.