4e committed the sin of not being what people expected. If you order a hamburger and you get served pizza, you’re going to be unhappy, even if you love pizza. It’s not that pizza isn’t good, it’s just not what you were expecting or in the mood for.
I say this not to disparage 4e, which I love, and not to say it isn’t D&D, which it is. Rather, I say it to acknowledge that 4e just didn’t resonate with a lot of folks who had an idea about what D&D was, who were put off when what the new edition of D&D wasn’t that.