Some would. Some did exactly that when Star Trek 2009 came around. I remember people saying that because it was an alternate timeline, it didn't matter and wasn't "real" Star Trek.
Personally, and I've said this before, I think making Strange New Worlds an alternate timeline does a disservice to both it and TOS. The connection between the two shows and between the characters makes both series better. Giving these classic characters rich and interesting backstories does nothing but enhance them in my eyes.
Uhura, while clearly an important and groundbreaking character for the 1960s, was never given much character development beyond her role on the bridge. We knew very little about her personal life, her struggles, or what it took for her to get there. Now I can watch TOS and see her differently. I know her pains, her struggles, and what it took for her to earn that place on the bridge.
The same can be said for Spock, Chapel, Kirk, and the others. Each of them has been enriched by what Strange New Worlds has shown us, in my opinion. Taking that away by declaring it an alternate timeline would do nothing but diminish those characters.