Hmm, could it be argued that this is less a snap judgement and more one of strengthening the long-term political and technical health of the OS? Rather than take the easier short-term path, which may eventually put Linux's metaphorical balls into a Microsoft vice, he would rather expose some pain now to defend as much as possible long-term autonomy. I would imagine this to be true given Torvald's historic ability to keep Linux healthy and viable in spite of one of the world's most powerful corporations.
Thus, in the short term, the user must perform some gymnastics to boot new kernels, but if this inconvenience is really that painful, it will create market disequilibrium that will motivate creative solutions. Some naive, off-the-cuff ideas:
- vendors pre-installing trusted root certs for Linux distros or a consortium of them,
- vendors making it easy to disable SecureBoot (physical switch?),
- vendors forcing SecureBoot configuration/opt-in on very first boot,
- UI, tools, or documentation enhancements to make local key management and signing easier, or
- simply a slightly more aware userbase (the same way phone locking/unlocking became a mainstream concept).