This is why discussion of objectivity when criticising art is so exhausting on the internet, and you're completely correct. You can make plenty of objective criticisms about art, but for some reason it seems to be a massive sticking point for so many people.
I honestly wonder if it's because people just don't like hearing negative facts about things they like. You can like and enjoy things that have objective issues, and there is nothing wrong with that.
My example is usually the movie Batman and Robin. Objectively, that film has a plethora of issues, but I still find it amusing.
If no objective criticisms could be levied at music, film, fine art, etc, criticism in these fields wouldn't be a thing.
The only question, in my opinion, is: When do enough objective issues stack up with a piece of art to make the whole thing 'bad'? As there is no definite metric for it, I prefer to just say that it has X amount of issues that can be demonstrated, rather than the whole is bad.