It never made sense to me how a group of peole could leave Kobol in warp capable starships and their descendants thousands of years later do not have that technology. And of course, we know it was just shitty writing, but if you add New Galactica to the mix, Bill Adama's fleet discarding their technology and starting over, would make 1980 make sense.
In one of the deleted scenes in TOS, Apollo explains that after the humans left Kobol and founded the colonies, they deliberately destroyed all of their technology. It took hundreds of yahren to revive even the most primitive ships for exploring space.
As for G1980, I always assumed that any continuation of TOS would regard it as a virtual reality simulation of what first contact with Earth would have been like if it had gone disastrously wrong.