Prostreet and The Run were the most maligned NFS games in terms of hype and fan reaction (I certainly remember the many diapers filled that came from Prostreet's reveal) but as they have aged, they've shown to be some of the best ideas the NFS has ever had.
There is definitely a point to be had in that ProStreet and The Run are some of the most unique games in the franchise, what with ProStreet dabbling with going legal and being ever-so-slightly more grounded in reality (apart from the occational bouncy suspension, though I'll put that down to the development cycle) and The Run basically being a movie but with added gameplay (..QTEs? Haven't quite decided if I like them or not). Now that I think about it, while I have played ProStreet recently because it's actually quite fun to do silly things like make a Honda Civic that goes ~250 mph or a Pagani Zonda wheelie machine, I haven't played The Run in forever. I guess that solves how to pass time this coming weekend.
I do, however, see a problem with the idea of essentially "rebooting" mainline-NFS for the fourth time: while it does muddy the waters even more in terms of trying to form a coherent identity (though I'd argue this is the 11th hour anyways, so who cares at this point), let's say whatever they do works out quite well. How are they going to handle that success? Are they then going to start an eternity of *that* thing overstaying its welcome and become the "true NFS"? Or will they have to switch it up entirely each and every game, in which case, is there a limit (pun somewhat intended)? No, really, would we be living in a world where Need For Speedboat Paradise (working title, pun and reference (no, not to the Burnout game) all in one) is a thing? I mean, there's only one way to find out..
The great irony in all of this, of course, is that Underground only happened because Black Box wanted to do something radically different. I feel like all sides of the argument can find a good quote in that.
Isn't that what Payback tried to do? One could argue it followed in the footsteps of The Run with its emphasis on a Hollywood Action Movie style single player campaign. It also brought dedicated offroading to the mainline series for the first time.
..while that is kind-of true (and good on you for emphasizing the "mainline" bit when talking of offroading), it's not just about how many new things you implement, but perhaps even more so how well they're implemented. Not only have I expressed my displeasure with everything regarding Payback's story often enough that one could write a book about it, but the offroad physics somehow managed to feel like even more of an afterthought than the entirety of NFS 2015.
To put it into a metaphor, Jurassic World: Fallen Kingdom has more species than any other Jurassic movie. That on its own doesn't automatically make it the better movie.
Also, technically one could argue that Payback ripped all its gameplay from the pages of Most Wanted 2012 and, by extension, Burnout Paradise. I'll leave it to your individual interpretations to decide if that constitutes as a "norm".