I think the real question is whether it's as hard or harder than just playing (since this is the alternative to participate in the game)... My thoughts are for the lion share of ttrpg games out there it is
I also notice, though I could be wrong in my interpretation, that you seem to be inferring that only a minimum bar achievement in GM'ing is necessary and I find a few things wrong with this...
1. If that is the bar and the GM consistently stays at that bar... he probably won't have a game for very long.
Why not? If they're having fun, this is fine. If they aren't having fun, that's a completely different question from how hard GMing is. Again, this goes to the accretion of expectation and tradition built up in certain segments of the hobby rather than an actual evaluation of how hard it is to run a game of D&D. Sure, it can be very hard to live up to
this table's expectations, but that's that table, not GMing.
2. It's still MUCH easier to attain the minimum bar for playing a TTRPG than running it.
Oh, that very much depends on the game system. For D&D, I'll agree that there's extremely little expected of the players in the tradition of play that has built up. But, that's not actually in the rules as such. The rules say that player should be actively engaging the situation and coming up with actions which the GM adjudicates. Depending on the fiction, that can be very demanding. Or not. The tradition is usually to put all of the effort on the GM's shoulders, but that's not required.
3. You seem to assume that your method of running games (I'd be interested in seeing you lay this method out in actual concrete terms as opposed to just countering individual points) will be easier for a GM when in fact there seem to be hints that it probably won't be... or at least only for specific DM's. As an example your method seems to rely on alot of improv, but that's a skill not all new DM's may be good at or even have (again why I'd like to see this "easy" method laid out in concrete format).
Oh, no, I work very hard for my D&D games. I work that hard because that's the expectation of my table and because, usually, I enjoy it. But, I recognize that that's my choice, not a requirement of running a D&D game. And, when I GM Blades in the Dark, I show up at the table with no prep, I wait for the players to start driving the action, and I react to each thing individually, building up the game by pieces. It's super easy, and my players end up doing as much work as I do. So, no, the difficulting in GMing is largely due to choice and the traditions and expectations built up around the games played rather than an actual, required, difficulty increase.