Seems to me CAs have intermediate certificates and can rotate those, not much upside to rotating the root certificates, and lots of downsides.

1. These might need to happen as emergencies if something bad happens

2. If roots rotate often then we build the muscle of making sure trust bundles can be updated

I think the weird amount they are being rotated today is the real root cause if broken devices and we need to stop the bleed at some point.

Five years is not enough incentive to push this change. A TV manufacturer can simply shrug and claim that the device is not under warranty anymore. We'll only end up with more bricked devices.

Isn't this the whole point of intermediate certificates, though?

You know, all the CA's online systems only having an intermediate certificate (and even then, keeping it in a HSM) and the CA's root only being used for 20 seconds or so every year to update the intermediate certificates? And the rest of the time being locked up safer than Fort Knox?

Those are weaknesses. It’s also that a root rotation might be needed for completely stupid vulnerabilities. Like years later finding that specific key was generated incorrectly.