Can I just remove those extensions?

Hi,

After the latest MacOS software update any system extensions that aren’t built into programs/apps will be automatically removed. However if they are built into a program/app then they will just be blocked and there is need to worry about them.

So to sum it up; Most system extensions will be automatically removed and most of the ones that haven’t been removed are built into apps that still need to updated and the only way to remove them would be to uninstall the app. So yes you can remove them (by uninstalling the app/program) but most if not all of the system extensions will be automatically removed over time.

Cheers and stay Safe

Those "extensions" that were installed on a past operating system are now no longer removable by you because they are on a read-only, signed partition containing the operating system.