Typos and brainfarts are one thing; I'll mark them out with extreme prejudice and specifity. But what do I do if I think that, say, there's stilted dialogue? I can point out exactly which ones I think are awkward, and usually fixing it isn't a complicated process (read it aloud and tweak it until it stops sounding awkward), but that's still not concrete 'do this, not that' advice, which might be, say, 'ins 'that' here, replace this proper name with a pronoun, split into two sentences here'. And this sort of technical, passage-and-lower level of problem is the *easier* sort to offer advice for; I can tell you that your pacing's too slow and getting bogged down in details, but I feel like I'm overstepping the mark if I tell you exactly what I'd be deleting and what I'd be snappifying.
Maybe I'm paranoid about this and over-thinking it. I don't mind close attention that comes with ready-baked suggestions (which I may or may not take) in my own writing. But, yeah, I do feel like editors have a duty to not let their voice drown out the author's.