True20/Blue Rose is a system I want to love, but don't. Blue Rose is one of the very few modern RPGs where I actually own the physical book as well as the PDF (including the most recent edition), but I feel like mechanically it is in this really awkward place where the system is a bit more of a "gritty fantasy" game than it wants to be, and it's also somewhat complex mechanically and puts a lot of weight on players to understand the system to build and play their PCs, when I feel like maybe maybe a lighter, more narrative touch was warranted for the subject matter. I strongly suspect that if it was post-Apocalypse World/Dungeon World, they'd have used that as the basis instead of d20, given the choice.*
* = I think what that illustrates though is that a lot of games are just using "the new hotness", rather than the best tool for the job. Not really a criticism, more a fact of life. Tons of AW/DW games might be better off with different systems too.
Blue Rose probably is more gritty than it wants to be, but I don't think that this is a weakness in itself of True20, which is more generic of a system than Blue Rose. True20 does not try to be Romantic Fantasy. This is not to say that True20 is without weaknesses, because it does have plenty of issues.
IMHO, I don't think that Green Ronin would have designed Blue Rose with the PbtA Engine (or Fate)* because I see Green Ronin as a company that is (almost too) heavily rooted in its d20 past. It can't quite escape that cord. Even AGE feels like a d20 game that is instead played with 3d6. And you don't really see Green Ronin designing much in the realm of PbtA and Fate either. There is the standard Fate conversion for their Free Port setting, but not much else.
* I believe that one can find a fan conversion of Blue Rose for Fate, though I don't think that one exists for Powered by the Apocalypse.
I'd much sooner run some sort of gritty low-fantasy campaign with True20 than I would actual Romantic Fantasy.
I have frequently used True20 for Sword & Sorcery, Psionic Fantasy (Dreamscarred Press's Third Dawn), Science Fantasy, and a number of other genres. My main problem nowadays with True20 is that it retains a lot of the weaknesses and fiddly bits of 3.0/3.5 style feats, talents, and skills, which permitted its existence under the d20 OGL. So it almost feels like a relic that needs updated to a sleeker, modern game design.
I'm not very keen on AGE either, despite thinking maybe that would be cool.
IMHO, the AGE System could use a Second Edition. The Dragon Age RPG, which served as the basis for Fantasy AGE, was designed and balanced piecemeal in small chunks, which means that it fares better in early levels than later levels, and it has a number of glaring weaknesses in its system that have been caught even by its ardent fans on the Green Ronin forums. But I don't see a good revision of AGE happening anytime soon, particularly after Modern AGE and The Expanse for AGE. Furthermore, the AGE system is nowhere nearly as generic as its arguable True20 predecessor.