And then it really hit me. D&D had become a beast.
With respect, it has been a beast at least since 1e, and possibly before. Maybe things were not this way for you personally, but speaking broadly: Rules-lawyering arguments and taking a ton of time to get through a combat were there from the start. Nor are such issues a D&D thing - let yourself settle into that nWoD for a while, and you'll find it has lots of room for the same detailed min-maxing as you see in D&D.
Maybe your memories of the individual minutes are crystal clear, but I think most of us forget that way-back-when our play had all the same issues. 30 years ago, we were arguing over rules, and getting annoyed at each other because that other dude was acting like a jerk and killed our characters, and played favorites among the folks in the group, and... simply put, everything that could have been bad in a game happened back then, too. 30 years ago was not some glory day when games were prefect, I'm afraid.
Now, we have a more sophisticated view of our activity. We have names for "spotlight time" and "rules-lawyering" and "social contracts" and such. Having that framework changes our perceptions of games we play today, but doesn't really touch on our distant memories.
On top of that, simply put, nobody is the same person now as they were 30 years ago. People change. This is natural. It is thus natural that what we want changes. The things we were quite willing to spend oodles of time on quite happily back then are anathema to us now. It is like... developing an allergy after long exposure. And human memory is not as exact as we'd want it to be. If we are not careful, we don't take the perspective changes into account in our remembrances. We don't recall thing X bothering us, so it must not have existed! It is more that we have forgotten, or even kind of enjoyed X at the time.
Which is not to say that you can play D&D today and like it just as much. I'm more saying that maybe you're pointing the finger at the wrong root cause. Your burnout may not be because the game has changed and become a bad thing. But *you* have changed, and now no longer fit the same game and playstyle. You should be changing up your game like you change up your wardrobe, man! Are you wearing the same clothes you did 30 years ago?