It's weird... up until a few weeks ago, everybody shot 1080p (at least all the big name Youtubers) because 4K was too big and difficult to edit. People just wanted full frame 4K on the Canon... and now they have it... normal 4K doesn't overheat on the R5 at all, and it's full frame and though not as sharp as HQ mode, it's still better than 4K on the EOS-R.
The new modes, like 4K60/120 and 8K overheat, as does the super HQ oversampled mode... these are things that didn't exist in full frame before for the most part except for the new (and expensive) 20 MP 1DX3. XT4 overheats in 4K 60 after 14 minutes and that's a small sensor. All of Sony's cameras to date overheat in 4K (Daniel Schiffer announced last week his A7III overheats in 4K30 after about 20 mins). Sony A7SIII was just announced and it has heat issues, but much better than anything before... and that wont be out for 2 months, and it's a crippled 12 MP camera.
I think people have been given an inch and are taking a mile here.
But with that said, many are not having heat issues in the real world (ie, not sitting the camera in the sun and letting it run nonstop to test it out, or filiming 8k on movie sets like Armando Ferrera). DSI PICTURES has a great Youtube channel, he filmed "all day long" in 8K raw and had no overheat issues- the overheat icon didn't even pop up once! And he wasn't shooting in the arctic, but rather in Australia, where daily temps are about 15-20c (normal room temps, or a nice day here in Canada).
Anybody who wants to shoot uninterupted 8K for hours, you will have problems. People who need to shoot 4K 120 for more than 30 mins nonstop, I think you may need to rethink how you shoot (that's 2 hours of super slomo).
I think 99% of the issue is the whole "Sony vs Canon" crap. The Sony people were really butthurt this year when the R5 was announced. I know at least a dozen who were ready to sell all their gear and get an R5 because "Sony was stagnant and letting us down".
Then the A7SIII was rumoured, and the Sony hype machine (ie, Youtubers like Gerald Undumb and 10000 Sony Ambassadors who only care about video and vlogging) set into action and the war rages on.
I would love to see a firmware to maybe double the heat limits (Sony does this in their cameras like the A7SIII, it increases the temp at which the camera shuts down but at risk of lockups or file corruption (Dan Watson had this happen to him on the A7SIII)). But I would more like to see that 30 min record limit removed (I thought after 2019 that wasn't necessary?), and even more than that I hope they follow thru with the promise to add 1080-120 (how did they not include that?!) and Clog3 in the next firmware.