The meat of my critique is that you're trying to tell me that you know why I switched from 4E to 5E better than I do
I'm offering a theory about what was so different in 4e from prior and subsequent versions of D&D when it was perceived as 'not really D&D.'
Not really much to do with the folks doing the perceiving nor their real or professed ratiocinations for doing so.
Just identifying the significant difference that corresponds.
I will not use the phrase "Primacy of Magic". I will not give any explanation that could reasonably be called "Primacy of Magic".
The Primacy of Magic in D&D is a common thread - except in 4e - it really doesn't matter how you feel about that. I may have, like, just put that label to it, but it's pretty obvious. Love it or hate it or ignore it: it had been there for a long time, it was briefly absent, it's back. It correlates with that discontinuity - a time when D&D wasn't really D&D, and Pathfinder had to step up an /be/ off-label D&D.
You will get a broad variety of reasons.
I mean, I'd /heard/ a very broad variety of reasons for judging 4e, uniquely among all editions of D&D, to be NOT D&D. Many of those reasons are just outright nonsense, or fail because other eds not so harshly judged, shared them. Those that stand tend to boil down to class balance or rewards for system mastery - the latter issue isn't something that's been consistent in all eds, the former is.
Now, sure, it's just a correlation, but it's consistent.
I don't buy that narrative. I dispute that Primacy of Magic is a sufficient explanation for the failure.
Try thinking about it the other way-round. That continuity the OP mentioned? The break in that continuity was 4e. That break would still have been there even had it been commercially successful in spite of the nerdrage (and so many other factors went into the failure, if they'd /all/ been different that doesn't even seem implausible).
What did it do /so differently/ that coincided with that? Not to the appeal-to-popularity 'failure,' but the rejection of it as "not really D&D."
Presentation? 1e presentation and 3e presentation, for instance, were very different from eachother, too, as was 0e, as was BECMI vs AD&D. The nerdrage was minimal by comparison in all cases.
Inverting saving throws into defenses? 3e inverted (un-inverted) AC, broke out Touch AC, re-defined save DCs by spell level - no major issues. The 'power' rubric? Clerical prayers had long used the same mechanic as conceptually-different MU spells with no issue.
Something else besides the status of magic made it "not D&D" to the people who were into that sort of thing.
What "something else" would that be? What broke the OP's continuity of D&D in 2008, if not the unprecedented treatment of martial classes, the unprecedented powering-down of caster classes, and the near-trivialization of magic items?
What, that prior eds hadn't already done, nor 5e retained in some bowdlerized fashion?
Furthermore, the perception that it was "not D&D" would have been immaterial to all the potential new players with no preconceptions about D&D whom it didn't attract and whom 5E did
Actually, the perception of continuity with past versions quite material to a game that trades so heavily on it's legacy & name recognition.
But, again, it's not about how that perception affected sales or fueled appeal-to-popularity arguments, but that the perception existed, and was so virulent & persistent.
And, yes, the status of magic seems like a very real candidate for that difference. The various details people complained about were generally present in other editions - some of the most divisive, even still present in 5e - without significant issue.
Take martial healing (and, indeed, surges & overnight healing) - in 4e, when it was balanced with clerical & other magical forms of healing, it was horrifying, the very concept was supposedly intolerable. Yet, in 5e, it's (all, counting HD as Surges) still present, but martial healing is much weaker (as are HD relative to surges), you couldn't depend upon it to keep a party going, you /need/ the magical healing the Cleric &c, again - and, while the martial-healing /concept/ that was supposedly so intolerable, before, is there, the 'problem' with it isn't: that continuity with all other Real D&D is restored.
And as a side note, for my money the nonmagical ranger was one of the things 4E did right. So, again, Primacy of Magic is really not looking like a good explanation for me.
The Primacy of Magic /requires/ non-magical options (attractive ones, or 'traps,' at that).
"If everyone is special" (magical), "then no one is," afterall.