All of it was in there to give fans that hit of sweet, sweet nostalgia.
No. When I was looking at the DSC Klingons, the last thing I was thinking of was the '60s Klingons. You might've been thinking about the '60s Klingons, but I wasn't. When I saw the DSC Mirror Universe, the last thing I thought of was the TOS Mirror Universe.
You use that word over and over and over and over again, but you always use it wrong. If it was the TOS Klingons in DSC, if it was the TOS-style Mirror Universe in DSC, then I'd agree with you. 100%, I'd agree with you. But it wasn't. Those felt nothing like TOS.
"If Memory Serves" was TOS nostalgia.
SNW is much closer to feeling like TOS than DSC Seasons 1-2 were, so I'd also put that further up on the "nostalgia" scale. Hell, I would put the Kelvin Films higher up on the Nostalgia Scale than Early-
Discovery was. The Kelvin Films felt more like the TOS Era than
Discovery.
DSC, much as I like it, was an odd series to be a prequel. That's why I was glad it jumped to the 32nd Century.
As far as the whole Canon Debate, it doesn't change what I like. If they officially said the series were in different timelines, my stances on everything set in the TOS Era or Earlier would still be:
TOS --> Love it
ENT --> Don't like it
Kelvin Films --> Ehhh...
DSC S1-S2 --> Love it (same goes for the rest of the series)
SNW --> It's okay