The bottom line is, the studio sets the rules. They are the ones deciding what is and is not set within any given timeline, and their policy is that DSC, SNW etc are all set within the same original timeline as TOS, TNG etc. Not everyone will agree with that, and that's fine, but when it come to official policy, that's the policy.
I absolutely agree with this, have said as much within this thread, and went on to lament that most folks don't actually listen to the studio folks who convey the policy rules for the "Star Trek Universe".
Indeed, broadly speaking, the issue of obvious discontinuity is a bit of a sideshow. If you alter the universe before adding to it, then it could be a show with perfect continuity created using a time travel device allowing it to be genuine new material from 1967 written by the Genes, acted by Shatner and the gang, et cetera . . . but it would, inevitably, still be alternate.
Such a time-travel-produced alternate just wouldn't be so in-your-face about being alternate, and nobody would really care about the technicality.
By contrast, the obvious discontinuity stuff acts here as an emperor's nudity.