I know the youtuber and if you're not familiar with her style it might come across as harsh and she was a pretty crass way of expressing things, often making self-deprecating jokes. It's not for everyone.

I believe she made it very clear it was her opinions and her opinions only. So. It wasnt any sort of ranking, it was just a personal thing.

It is pretty clear with what she enjoys which is: romance and smut. That kind of booktuber draws an audience that enjoys the same thing. Or her humour. Comments will reflect that.

Trying to draw some unbiased conclusions as to what is liked and not in fanfics is not an answer you'll find in a booktubers comment section.