The NX-01 Enterprise already had holo target shooting, the NCC-1701 Enterprise had a room that could make a hologrpahic environment. If you combine these two it seems fairly reasonable to me that you could end up with something like the DSC holodeck. Furthermore Janeway claimed in "Flashback" that some of the 24th century technologies were around in the 23rd just a lot less evolved. I interpreted this difference of the lack of true holographic interactibiltiy as seen in the 24th century where you could talk with holograms. Here they just react to energetic impulses.
The problem with this is that in Encounter at Farpoint and some other early episodes, the crew was superduperIMPRESSED with the holodeck. They thought it was the most amazing thing, like they'd never seen one before.
If holodecks were such old hat even during pre-TOS, the TNG crew wouldn't have had that reaction over 80 years later.
I may be biased here because I loved most of the Sarek stuff (especially in "Lethe") but I thought his behaviour wasn't so far removed from the future Sarek we see in TOS. What it does change is how we perceive his past. In TOS we just assumed that Sarek hated Starfkeet from the ge-go but DSC provides us with more of an arc for him. His estrangement with Spock began with his chosing of starlfeet over the Science Academy. He previously made it impossible for his adopted daughter to enter the Vulcan Science Academy, based on an illogical choice, because he wanted Spock to enter. Once he didn't the illogic of his actions backfired on to him and because Vulcans suck at dealing with emotions he projected his guilt onto his children. Once he actually managed to make peace with his daughter he also supported Starfleet in a terrible immoral, illogical, decision. Unable to actually cope with the situation because Vulcans suck at emotional stuff he once again projected his own failure onto Starfleet which also provided him with a convenient excuse to not talk with Spock about the incident that started it all, his choosing Spock over Burnham for Vulcan Science Academy application. I know that most of this is speculation on my part, but I think that DSC makes Sarek into a far more interesting character than he was before (hence why I like to write long paragraphs about him

) so I think it fits fairly well.
There is no way that I will ever watch TOS Sarek and mentally include Michael Burnham as a factor in his thoughts, speech, and actions.
As for Sarek adopting a human girl... sorry, but but it's not a new thing. Fanfic writers did that already, 50 years ago. I probably have some of those stories among my collection (I collect '60s/'70s/'80s print 'zines, and haven't read all of them yet).
"Being different worked in their favor..."
Really? Is that why in the second season of TNG they brought in the female McCoy close character of "Dr. Latherine Pulaski" who (exactly like McCoy):
- Didn't trust transporters
- Called herself an "old country doctor"
And was brought in specifically to try and resurrect the Spock/McCoy 'friendly jabs at each other - which failed miresably because of the way the TNG writers had developed data:
IE On TOS the relationship worked because Spock wasn't that naive and he gave as good as he got and held his own very well.
On TNG, because the writers (IMO the the character's detriment over the years) kept Data naive to a point that when Puklaski verbally jabbed at him, it came across like a nasty old woman (with a superiority complex) badgering a young child without the social experience to understand or give a similar come back.
There's a fannish explanation for this: Katherine Pulaski is Leonard McCoy's great-granddaughter, who spent a lot of time with him. He inspired her to become a doctor, and she took on some of his traits (as some people do who spend a great deal of time around people much older; I speak from experience, having been raised by my grandparents).
She had the benefit of his knowledge and old-fashioned "country doctor" ways that don't accept that the computer is always right, and when the computer goes down, she still knows what to do when her colleagues give up. That's not to say that she didn't also absorb some of Leonard McCoy's prejudices, but by her last episode, she had started to work on changing those.