women diplomatically describing a man who they are not sexually interested in as a "nice guy" or as "nice" precedes the internet. it's not an intentional dig, it's indicating that the guy is not projecting (in their estimation) other, more scintillating or captivating qualities -- he's not weak per se, but has a weak or unaffecting personality.

as with literally everything, context matters. if someone refers to you as nice, very earnestly, or after you've just done something nice and thoughtful, it's nice to be called nice. but, if the situation is more like, women are speaking among themselves about you and one can only muster a respectful, "oh, uh, he's a nice guy," or, you're in some kind of approach with a woman and really feeling her and then she says, "you know, you're a real nice guy . . ." while pulling away, they are signaling that there isn't that attraction there. again, it's not that "nice" denotes weak or unattractive, it's that, in such situations, to be referred to only as nice, a comment of perfunctory respect, instead of anything else (e.g. handsome, passionate, fascinating, funny, so smart, etc), implies that the speaker doesn't find the guy to possess such qualities.

but generally, it's nice to be nice, and there's no need to overthink it, and if you think you're spending too much time on the internet, just do less of that.