Depends entirely on the context. I wouldn't consider doing it if I didn't think that feedback was welcome, and I would never do it in any way that did not make it clear that it was a suggestion, and reflected a personal preference and/or personal experience.Have you considered that cropping someone’s photo could also be viewed as an insult?
Unless of course the crop suggestion was purely practical and functional - which only really applies to things like catalogue or journalistic photos.
I'm prepared to learn that "naive" has a special meaning outside of common use that I'm not familiar with. In common use it means uninformed and unsophisticated, and is generally used as a pejorative when applied to those who have a fair amount of knowledge and experience, even if not in an academic setting.I’m sorry you took it as a personal insult.
“Naive” needn’t be as negative as you seem to think.