I think people notice, and if they are polite they keep negative opinions to themselves. So I might be walking around thinking no one notices when really they might notice and not like! The people we think notice, because they say something nice, may just be the few whose opinion aligns with ours.
The more I look at and try to learn about fashion, the more I think it is all opinion. I'm not sure what all goes into forming those opinions because it is so complex, but there is definitely no actual right or wrong that I can tell. Angie's posts formatted like Friday's Transitional one is just one example...for each outfit some will like it and some won't. Any time someone posts a keep/return the opinions are all over the place. In IRL the "that doesn't look good, you shouldn't wear it" contingent probably just keep their mouths shut. Hopefully! I can watch a YT video where the person is just loving their soooo cute new whatever and I will think it looks bad. Opinions.
Once I was out with a friend and she was wearing something Chicos from about 15 years prior and she got so many compliments, many strangers stopping us to say they loved her outfit. I was wearing something that would have met with more approval on YLF but no one said a word to me. I doubt it was that they noticed her but failed completely to notice me standing right beside her. They noticed me but I didn't make them happy. Opinions.
I do think people who frequent a fashion board are looking for a standard of "rightness". I don't think it exists in any objective way. It's all opinion.
I may have gotten off track from your question...I guess I'm just rambling on something that's been on my mind for awhile. But back to the question...yes, I think people notice. If it seems like they don't, maybe they just don't care that much about what they see and are politely keeping it to themselves!