I'm moving this over from "Rolling Characteristics in 5th Ed." as it deserves its own thread.
PROVISO: I have only recently attempted to enter 5th Ed. and have thus far read only the main book. Material in subsequent 5th Ed. sourcebooks which may be relevant is outside my present purview and thus has not been factored into my perspective. The following is based on my visceral reaction to 5th Ed. "Ars Magica" itself.
The magnified negative effect of the Dominion on Magic and Faerie must produce a corresponding influence on the evolution of the behaviour and culture of those Realms adversely affected by it. In 5th Ed., urban Covenants are greatly weakened, whereas before it was a "nuisance" that social Magi might be willing to overlook. As the Dominion spreads, it steals more and more of the Power which belong to Magic and Faerie. It thereby becomes an adversarial force which is to be opposed, not one to which the Order surrenders (the statement that anyone causing trouble with the Church gets Marched by the Order is an egregious example).
It is worth noting that my most recent 4th Ed. Covenant, Bridgedwell, worked to reconcile Magic, Faerie, and the Dominion. The Church of St. Brigid was the focus of the Covenant, and its Bell of Bright Faerie Iron was enchanted to destroy any Demons who came near. The idea was that there might be a way for the three Realms to coexist and complement one another. St. Brigid, obviously, is the converted/conflated form of Bridget, the Celtic Goddess and a great Faerie Power. She was also called "the Second Mary".
In 5th Ed., this type of endeavour would never have been attempted. The countermagical deadening caused by the Church would have been so extreme as to prevent any meaningful cultivation of a mutually tolerant coexistence. In 5th Ed., one wonders how Andru could ever become Primus of House Jerbiton when his deference to the Church and Susceptibility to the Divine Flaw would effectively make him magically impotent in the presence of that which he adores. Somehow, I can't see Magi following his example.
This creates a vicious cycle. Magi shun the Dominion because it severely weakens them. Magi should therefore oppose the Church as well as probably Judaism and Islam. Magi drift further and further from the Divine. If the simplistic explanation of Infernal Auras holds (i.e. regular "sin" in a place can eventually produce it), even the casual "sins" of the Magi and Covenfolk will become magnified over the generations until Covenants are sinks of Infernal Auras interlaced with Magic.
Retroactively stripping Magic Resistance from ALL non-Hermetics after 16+ RL years and 4 Editions violates any understanding of the balance of power within Magic. The fiat saying that Charms Against Magic, also a staple of the game from the start, can't work compounds matters. It also "fixed" a problem that never existed. Hermetic Magic ALWAYS had stronger Magic Resistance than others due to their Parmae Magica plus Form scores. They were stronger and more versatile, but "hedge" traditions could sometimes hold their own and weren't pushovers for starting Magi. "Ordo Nobilis" did go to ridiculous lengths in extending Magic Resistance to nobles; that could have been fixed without violating so many other elements of canon. Magic, heretofore shared by many traditions with the Hermetic tradition foremost among them, now belongs overwhelmingly to the heirs of the Hermetic Founders.
Fifth Ed. shatters the balance of Powers among the Realms. The repercussions on the milieu cannot be ignored. This, to me, is its gravest offense as a new Edition. Its mechanical changes may be interesting and even useful, with some quibbling over certain points, but the above are major, world-altering changes which constitute and almost unbridgeable gap with previous editions if allowed to stand as presented in the 5th Ed. main book.