I thought of it a bit more, and I think there may be something specific to you that may have an impact.
This is only my personal feeling, I have no idea if it's a shared feeling, but it may be something you'd like to think of.
I've realized that you are not very confident and you tend to often belittle yourself and your art. Well, in my opinion, that may have an impact on the feedback you get, and especially, on what kind of art gets feedback.
Let me explain: when someone see one of your sketches, and see you are saying something negative about it, they may think you are disappointed in posting a sketch rather than a finished drawing, or they may think it did not go past the sketch stage because you did not like the way it ended up looking.. So the person looking at the sketch won't necessarily be bothered by the negative things you said about it: they will just see it as "that sketch is an unfinished, not completely satisfying work', and they won't feel weird for liking in anyway, because they can expect to have like it even more if it was finished/a even better version.
Now if it's a finished work that clearly took you a lot of time, efforts and thinking, but that you also speak negatively about it, it puts the person who look at it in a very uncomfortable situation. First, they may think it's way better that what they could do, so they may feel a bit offended. Second, if they like it very much, they may feel uncomfortable and feel they did not understand what you wanted to do. Because if they like it, but you don't, that makes it sounds like they did not get what you were going for. It kind of create a gap between you and them, which is not a good thing to get comments or other feedback. People don't like feeling uncomfortable or feeling that they are misunderstanding something.
As I say, may just be my personal feeling.
Another thing I would like to add is that it's not impossible that your ratio of feedback is skewed in favor of these sketches, simply because these sketches are particularly relatable to a large amount of people. Obviously you'll get all the BL fans, but because your drawings are cute and tame, I think they may have appeal to a more general public. I mean, some of these are really adorable and should be relatable to anyone who owns a heart (well, and who's not too opposed to cuteness either I suppose 
).
