"It's about the future, Madam Chancellor. Some people think the future means the end of history. ...But we haven't run out of history just yet. ...Your father called the future ...'the undiscovered country'. ...People can be very frightened of change." - Captain Kirk, TUC
People don't like change.
I don't think it's about being frightened of change as quite a few people who like the old timeline would rather see new characters and situations there. In some instances, it's a desire to go forward with Trek rather than backward, so they do
embrace change, but perhaps not the kind
of change the new movies have brought.
People like the old universe they grew up with. Don't try to over think it. It's as simple as that.
Truly. People like what they like. 'Nuff said.