Its easier for me to speak of Dragon Age, since I ran it and not just read it.
The easily addressable one (which they have fixed as at least an optional in Modern Age) is that the level elevating hit points do not work at all well with the damage absorbing armor, especially since the ways to raise damage output are pretty limited.
The other issues is that there's sharply limited ways to show any sort of vertical increase in ability; there's plenty of ways to show horizontal increase, but pretty quickly it can turn into "Yeah, I can buy this Talent or this Focus I'm probably never going to use). And connected with that, if you don't have the elevation in hit points, there's even less way to show any increase in defensive ability (a couple Talents can help, but in an even more limited way than on the offense).
As I noted, none of this starts showing its ugly face until you hit about 8th level (though at least in DAGE you also had blatant winners and losers among the Talents and the Spells; I'm not qualified to judge how true that is with FAGE).
Those seem like exactly the sort of things I don't like. I guess I'll see whether the new edition fixes any of that.
I have played a fair number of campaigns of Fantasy AGE (Titansgrave) and partook in the Fantasy AGE Core playtest, running a number of sessions with the playtest materials. I do not have any experience with Modern AGE, however, apart from cursory glances in the books, since my past players prefer more standard fare fantasy. I don’t mind answering questions about FAGE based upon my own experiences running the game.
I will say that I personally find the criticism of AGE providing horizontal progression over more vertical progression to be a feature rather a flaw, though I can understand how someone who prefers the vertical progression of, let's say, Pathfinder 2 or D&D to be more to their liking would not find AGE to their liking on that front. There is a flatter power curve to FAGE. You will not find any magic on the level of Wish or even upper level spells in AGE. The "master" spells/arcana in FAGE would probably be about 3rd or 4th level spells in D&D. FWIW, I typically prefer this level of magic for a lot of my fantasy homebrews.
I do think that Modern AGE is the more polished version of the game. The upcoming FAGE Core Rulebook, however, desires to maintain backwards compatibility with the existing supplemental materials (e.g., FAGE Bestiary, Lairs Book, Campaign Builder's Guide, etc.) so it doesn't try to rock the boat as far as making adjustments to FAGE. That said, Fantasy AGE makes some changes to the Dragon AGE system, and there will be additional changes as part of the upcoming Fantasy AGE Core Rulebook. It is also introducing the Envoy class, which can be built to be more Warlord like and not just Bard-like. The four classes suggest that each will excel in different pillars of the game: i.e., Envoy (Social), Mage (Magic), Rogue (Exploration), and Warrior (Combat). Also, there will be some additional bonuses to damage and defense as part of class progression. And Specializations will now start at level 1.
Keep in mind that one reason for the higher HP is also a result of how Combat or Magic Stunts can enable extra attacks and/or damage. As characters progress, they will often be able to do some stunts more regularly or often. There are also spells and abilities that let PCs penetrate and bypass armor damage reduction. Moreover, there are mods that are part of the base game of Modern AGE and found in Fantasy AGE Companion that allow the GM to adjust the HP or damage, use a Wounds system, action points, or a Stunt pool. The game is almost effortlessly hackable IME.