The success of 5e is obviously a lot about branding and market dynamics. But playing it, and seeing others play it and get into rpgs for the first time, I think what it suggests to me is, to put it pithily, ‘system doesn’t matter.’ Or doesn’t matter to the degree and in the ways that some people think it does. There’s an element to a game system that affords a playstyle by simply not getting in the way. So, we don’t actually need mechanics for fantasy shopping. The character and world building prompts in the game do a better job, without rules, to give people the fantasy shopping simulator they desire. Making sure the ‘system has a say’ would make the experience less fun. When people are trying to perform, having to refer to mechanics can be disruptive. (Similarity we can say that critical role was influential for 5e’s success. But what makes dnd a good vehicle for that kind of game? What about dnd produces the Matt mercers of the world?)
With regards to character, I think the way that dnd evokes fantasy archetypes is a big part of why people like it. I prefer osr games with streamlined classes and races. But I’ve realized that is not what my players like. And from reading things online, I infer that most players are wrapped up in the backstory and/or build of their characters. They are not concerned with authoring the fiction of the world because they are in charge of authoring the fiction of the one thing they care about, their characters (and their character’s pets).