yikes
nervous shaking
hiding under a blanket
I guess my gaming experience is mostly in more "traditional" RPGs (read: D&D, Savage Worlds, Chaosium BRP). While trying to read a copy of FATE I purchased, the whole concept of the game went over my head. My PbtA games I've run went severely over the rails (I've been told I don't understand how to GM them). The other games you've mentioned I've either never looked at or never have heard of.
I think my primary difficulty with running games like PbtA and FATE (unless I completely misunderstand them) is that they strip control away from the GM and put it in the hands of a narrative "rules-lite" mechanic. You get things like: "You can't put a trap there and you can't call in reinforcements - unless they're specifically in the GM Moves you did during your prep. My character can't drop my sword because I have the 'sword is tied to my hands' Aspect."
Good grief. I think that you may be overreacting.
Fabula Ultima is not a PbtA game nor did I say that it was. If you are familiar with Vincent Baker or Luke Crane, you will hear the echoes of their advice and such, but if not, then you will probably be completely oblivious to the fact that it's there. When I say that FU contains the clear influence of narrative game philosophy from Vincent Baker and Luke Crane, it's mostly in terms of concepts, game principles, or advice on how to run the game rather than mechanics. These are things like following the rules, don't subvert the outcomes, emerging story, breathe life into the world, play to find out what happens, ask questions and build on the answers, making the stakes of failure clear before a roll, "the fiction," etc.
If Fate went over your head, that's fine. IMO, Fate doesn't do a good job of explaining itself as a game. (Condensed is slightly better.) Much as
@overgeeked says, however, FU does do a good job of explaining itself and providing step-by-step guidance.
Fabula Ultima has aspect-like Traits. Inn Fate or Cortex, we would call these sort aspects "
guided traits/aspects." A character has three traits (i.e., aspects): Identity, Theme, and Origin. There is instruction on how to write them.
You are not going to have a "sword is tied to my hands" trait in FU. In Fate, aspects do most of the heavy lifting. That is not the case in Fabula Ultima. Likewise, you are not going to have situational/scene aspects or the Create an Advantage action like in Fate. Instead, you are going to get players spending Fabula points to invoke their Traits ("Disgraced Master Swordsman") and/or Bonds (+1 Inferiority: PC 1; +1 Admiration: Church of Light; +2 Hatred: BBEG) to improve their rolls. Think of them as BIFTs from 5e that actually work as intended!
However, Fabula Ultima does NOT want the GM to present a pre-authored story or guide the players through an adventure path or engage in setting tourism. If that is what you want, then Fabula Ultima is NOT for you. However, that would also be the case for OSR. Or even the Alexandrian, which often advocates "prepare scenarios, not plots!"
Overall, I feel straightjacketed by these types of systems.
Overall, I feel liberated as a GM and player by these types of systems.
I'm a KoLC Patron, so I've seen a lot of their videos. Derek and I have very different views of PbtA, Fate, etc. Thus, when I hear during a system deep dive "it's simple to run," it concerns me that the GM advice is what they refer to on their channel as "fluffy b.s. time." My experience with PbtA is that the entire GM rules are "fluffy b.s. time" - like there are no rules that matter and you just write a paragraph and that's kinda what happens, but there's really no guidance on when you can do it.
Derek and his channel refers to mostly freeform roleplaying that is detached from the mechanics as "fluffy b.s. time." The GM rules for PbtA are
far from "fluffy b.s. time." Most PbtA provide pretty good advice on when and how to apply the principles of play, and that advice has only improved over time and iterations of PbtA games. Like if you compare the GMing advice between Dungeon World and Stonetop, the latter is leaps and bounds ahead in providing examples, elaborating on advice, giving tips, and even suggesting when to make certain GM moves!