Canon's mistake with the R5 Mark II is obvious. They didn't make enough mistakes. When the original R5 came out, the overheating issues made it the talk of the town — but nobody's talking about the Mark II!?
In all seriousness, though, I got the R5 Mark II to supplement my original R5 and it's been doing a great job overall. My only complaint so far is about the button info message that appears the first time you do review after turning on the camera. That'll probably be fixed in the next firmware update.
But seriously... 45MP, 30fps ES with pre-shooting and extremely minimal rolling shutter, plus most of the video complaints about the R5 solved? Plus other goodies like eye control? Honestly, until/unless they come out with an R5 with a global shutter, I'm not sure what would get me to upgrade from this. Like, needing to use an external recorder for video + the 30fps ES for baseball were enough to get me to the Mark II. But at this point... hard to top that. It's a far cry from the old DSLR days. And I still love those old hunks of metal.
At this point, the "aspirational" upgrade I might make one day is to go from my EF 70-200/2.8 L IS III to the RF 70-200/2.8 Z. But I have no pressing need to do so. The EF III is still excellent (as easy as it may be to forget it). Actually, in general, I think we live in a sort of unheralded golden age of great cheap DSLR lenses (still). A bunch of DSLR Sigma Arts can be gotten for not too much and are nearly perfect on mirrorless. Tons of stuff on the used market out there.
