It’s so bizarre to read this in the present, knowing how incredible TNG was, but I get it - the original crew WAS Star Trek to them.
The dedicated fans revived this series in syndication, well after it had gone off the air in 1969, and felt attached to the characters that they had obsessed over between then and the 1980s. Like modern fans, they thought that departure from what they knew would ruin it.
I wish I could go back in time and tell them that TNG is going to rock.
That’s actually why can rewatch TOS endlessly but TNG only occasionally. TOS is that light popcorn fare that’s entertaining but you don’t take very seriously. TNG is serious sci-fi that challenges the audience often with very difficult subject matter. The latter is objectively the better show but if I’m looking for something to throw on for casual fun, for me it’s TOS all the way.
Same, though there’s one i can really watch endlessly: TAS. Giant Spock melting minds with normal Spock always gets me.