But do you mentally TOSsify DSC or discofy the entire franchise to match?
Why do you have to do either? I don't have to do any grueling mental contortions to watch TOS and watch DISCO and accept that they're different chapters of the same story even if (for real-world reasons) they don't
literally look the same. I just go along with what the story is telling me.
If I'm understanding you correctly, you seem to be suggesting that movies and TV need to be held to a higher level of "reality" than other forms of fiction, but I don't see it that way. Fiction is fiction, reality is reality, and enjoying the former requires a certain degree of imagination and participation on the part of the audience, whether you're talking movies, TV, theater, novels, comics, video games, whatever.
To put it another way, visual discrepancies in Trek don't necessarily have to induce the kind of cognitive dissonance you seem to be worried about. Personally, I don't have to force my brain to impose one set of visuals on another. When I watch TOS, Trek looks like TOS. When I watch DISCO, Trek looks like DISCO. But it's still the same characters and continuity, just different cinematic productions made by different people in different eras, with the same characters sometimes played by two or three different actors as well. The artificiality is what makes it art, not reality, as it were.
That's just how this stuff has worked since the silent era at least, and on stage before that.