I’m not convinced that it’s impossible to build a modern OS in a way that’s properly modular and allows most functionality to be disabled entirely (as in never even loaded into memory).

Windows almost categorically can’t because it’s only ever been developed organically and is pathologically backwards compatible, which keeps it forever tied to past design decisions.

Linux could get a much closer but is hamstrung by monolithic kernel design which puts more functionality there.

You’d need a clean sheet design which positions most subsystems as discrete components.