It's mostly considered a "big jump" because Sony cameras have 60MP, Canons don't.
The real big jump is the quality attained by recent sensors, whether 24, 30, 47 or 60 MP.
But a 60mp sensor would be
very undesirable for shooting video.
Look at these resolutions:
Sony 60mp: 9504 x 6336
Canon 45mp: 8192 x 5464
8K DCI: 8192 x 4320
4K DCI: 4096 x 2160
If we look at those horizontal resolutions, it's clear why there's a big problem with 60 mp. Using the Canon, I can shoot full width 8K and I can shoot full width 4K by simply pixel doubling. But with the Sony, the camera must either crop substantially (14% horizontal) or else scale very irregularly in both 4K and 8K modes.
You might think that it's no big deal to simply crop, but now the lens focal lengths will all be off. If you're a casual video shooter, this doesn't matter, but for serious work, it's not an acceptable solution. The R5 Mark II will likely be an outstanding 8K video camera, but if it were 60mp, it could not be.
Maybe you only shoot stills, but we are many generations into the era of "combination stills/video camera." The 60mp resolution of Sony is a huge disadvantage for video shooting. And, from my experience with the R5, I would not like to jump to 60mp for stills, either, because of the performance impact it would have on my workflow. It took me quite a long time to get my hardware and software working fast enough for 45mp, but admittedly, that's just me.