There are plenty of things that I would consider decent quality that I don't personally care for. Take the movie Snowpiercer for example. A lot of people thought it was a great movie, I didn't. I don't go on forums dedicated to the movie and tell people how it was a low quality movie because it's not true. The the acting and effects that supported it were high quality. The fact that the movie just didn't work for me didn't make it low quality, it just means it wasn't the movie for me.
It's fine if you don't care for the game. But every time people assert that D&D 5E is low quality they're also implying that people like me and everyone I play with who enjoy the game are just too stupid or willfully ignorant to know better.
Nothing's perfect and no game is going to work for everyone. I've never said there aren't other quality games out there, even many that simply never became popular. On the other hand saying that just because I, and millions of other people, think 5E is decent quality it's somehow self serving and short sighted is just plain insulting.
I accept that something can be a quality product even if I don't care for it. I simply respect that other people value different things. I don't think respecting other people's preferences, even when I disagree, is all that hard.