3e has a major flaw that hinder it becoming massive in popularity like 5e. 4e has the same one. System mastery. Both are so complex in their mathematics and designed with system mastery in mind, that you are almost encouraged to build a game breaking character as a reward, that it can be discouraging to new people. It’s also overwhelming. 5e is simple and remains simple. That’s also the benefit that it and 1e had over all other editions that let them be popular, they didn’t/don’t have a ton of materials to buy and play with. You have your core books and a small, small handful of additional optional materials. I hope 1D&D doesn’t get away from that model but with 5e increasing its supplement count the last few years I could see it getting out of hand in 4 years.