It's not insignificant. Dates are what allow history to exist at a conceptual level, to be organized in some comprehensible fashion. And Trek's cumulative history is what allows it to have any approximation of a workable continuity. If you start retconning things arbitrarily, and especially if you reduce dates to abstractions as simplified as "past, present, or future," you'll reduce Trek to something as incoherent as... well, for example, the Marvel Comics timeline, as
@Jinn already commented.
As for your second reason, it isn't one at all, since (as we've just been discussing!) Trek's history is blatantly, obviously
not the history of the world we live in. There are myriad examples of how and why this is so. I honestly can't imagine why anyone would put on blinders at this late date and try to pretend otherwise.
If the only way to keep Trek viable as a "franchise" is to throw away actual
Star Trek history... then fuck the "franchise," I'll take the history.
Seriously, otherwise you're tossing out the baby with the bathwater.
Sadly (but perhaps not surprisingly), many of the Trek novels over the past couple decades have offered far,
far better storytelling than anything that's appeared on screen during the same period as part of the official "canon." (This is one reason I'm not enthusiastic about the idea of a post-VOY series... it would almost certainly entail scrapping much or all of what the Litverse has developed, much as Star Wars did when the Disney films were greenlit.)
Well, some people are narrow-minded idiots. TV ratings (not to mention national elections) have been demonstrating that for a long time. So what? You can't ever please everyone, so if you're going to pick someone to stop
trying to please, let's start with the narrow-minded idiots.
So? You can imagine Spock said some other line of dialogue in "BOT," and the story does not change one bit.
(Note that I don't actually
buy that argument, at all... about either BOT
or the Eugenics Wars. But I've certainly seen people make it, in all seriousness, for the sake of defending "new" Trek over old. The examples are more comparable than you think.)