By their nature RPGs will always require GMs to do far more work than players. There are newer games though that require far less GM prep work (or almost none at all because the games are focused solely on narrative at the table and not focused on intricate rules/mechanics to adjudicate everything)
I also agree that 5E's success is in large part to a game that is much easier to teach and play than anything since Mentzer's BECMI sets (And probably easier- because of unified mechanics, higher always = better rolls, A/D vs. multiple small modifiers, etc.) but WOTC's adventure path business model makes for a large and intimidating burden for new DMs. "Here is 900 pages of rules, and oh yeah- here's another 300 pages of adventure material....have fun!" That will always be a barrier to making new DM's. New DM's need adventure material in much less intimidating "bite sized" pieces.. I.e. "modules"-however we know WOTC doesn't find that profitable enough. Products like Tales and Ghosts are a good thing IMO, but I believe that new DM's need more books like B1/2/3/4/5 and T1. Not more like POTA,OOTA or SKT.
As I have said many times- If in 1977 I had to learn the game from 3 giant hardback books, and a 250 adventure path, I would never have got into the hobby. D&D has become less intimidating for new players, but not for new DMs.