It depends.
A lot.
I work with people I do "trust" and my code-review is usually "LGTM" -- often without even looking. Most code doesn't go right to production and can be fixed if there are bugs (which I'm unlikely to find by looking at it, anyway.)
The things I look at are things that are hard to change in the future: big architectural decisions, schema (db and data format) changes and things like that.
More junior and newer people, I tend to look more closely and give more advice.
Personally, I get annoyed when people feel they need to critique something to make it clear they reviewed the code. In most cases, the feedback I get from reviewers is not consequential -- and just slows things down. But I have certainly had cases where the reviewer made great points and I changed the code to fit.