Yeah, but we know that Kirk and Spock etc are running around doing just fine in the Prime Universe...
No, they're not.
They got old, fat, and dull. Stuffy and boring. Kirk fell off a rickety bridge before delivering one of his bizarre line readings ("It was...fun") and croaking. Spock was last seen shuffling through a kind of aimless story about Romulus with a bunch of old guys and Denise Crosby wearing bumpy foam rubber heads. McCoy was wearing a garotte-like ascot for vanity's sake to hide his wattle, Scotty and Uhura were fumbling around with various unappealing menepausal sexual hijinks, Chekov had evolved from Bad Accent/Haircut to Bad Accent/Toupee and Sulu...who gives a fuck about Sulu?
They're not "running around," "doing fine," or being at all interesting. These new guys are a lot more fun now.