McCoy was in Encounter at Farpoint with one meta purpose - to counter the TOS fans that were campaigning hard to say that it ‘wasn’t the same universe.’

McCoy’s presence was a nice Easter Egg, but not much more. But he did the job of saying that it was the new Enterprise in continuity with the legendary ship on which he served.

Fans argued that because Roddenberry insisted on moving WW3 back to the mid 21st century as of Encounter at Farpoint, TNG had to be a different timeline.

TOS fans understood the Eugenics Wars to be the precursor to WW3, so they just didn’t accept WW3 was going to be another half-century away. Roddenberry’s directive was to always keep the Star Trek future in our future so WW3 had to be shifted to later in time and any specific mention of the date of the Eugenics Wars was avoided.

They also hated the carpet and many other things about the ‘luxury hotel in space’ Enterprise.

Yup, that happened and continued to happen until well into TNG season 3. The brigading Berman-era fans who rail unrelentingly against ‘Nu-Trek’ don’t sound any different, they’re just more visible than the 1980s fans that relied on mimeoed fanzines and Usenet. Fans that liked TNG kept quiet at cons until at least 1990, and vendors didn’t bring TNG merchandise.