A good user experience can be achieved by providing users with an efficient way to understand and fix problems that they encounter.
De-featuring a product to prevent users from ever encountering a problem reduces the utility of the product, which produces a worse experience for everyone, not just the ones who would have had a problem they couldn't solve.
Those who would have had a problem they couldn't solve will still ultimately have a bad experience, because it's their own pattern of usage, and not any defect in the software, that's ultimately getting them stuck.
Moving an "advanced" setting to a different interface is fine, but the release notes don't say that the JavaScript toggle was moved to about:config; the notes say that it was removed (and that user-set values will be reset to default, which, IMO, is an unacceptable thing for an update patch to ever do.)