A "recast" isn't a "reboot." This is another red-herring argument that I keep seeing.And I don't remember any character ever being rebooted, with the exception of Spock coming back from the dead.
The recasting of Saavik, with a radical makeup change, esp. eyebrows and eye colour? Zefram Cochrane's personality change? Tora Ziyal (twice). Senator Kimara Cretak.
And Neral, and Captain Braxton, and Admiral Paris ... I know, I know. But I see those more like "character recasts" than "character reboots".
Explaining the new Cochrane is a little more difficult, though. Maybe he had changed in all those years he lived on that planet with the Companion?
"Oh, look, a different actress played Saavik.... you must be having a stroke, continuity-istas!"
Not at all. It was annoying that the character was played differently, but the background of the character was never changed. She remained a half-vulcan, half-romulan, rescued by Sarek on an abandoned Romulan colony and raised from childhood by he and Amanda on Vulcan. She continued to have been sponsored for Starfleet Academy by Sarek, and mentored by Spock.
Now, if they'd gone back and said "she's full-vulcan" or "she's Spock's little sister" or "She's actually a Klingon/Romulan hybrid" or done anything like that... this would be taking the character into "reboot" territory. But none of that was ever done, was it?
The character was recast, and the new actress played the role differently. It was annoying, arguably a bad choice (though Alley's downward spiral at the time made it inevitable!), but it's not a "reboot."