I always thought it was a shame that the Director's Cut, which is what Paramount+ is remastering, wasn't originally done in 4K. The Director's Cut was released in 2001, and BluRays came along only five years later.
The original was poorly paced. It's said that they were packing in a lot of special effects that were to be used on Star Trek: Phase II, a follow-up TV series that morphed into the movie. Some story got sacrificed to make time for those extra effects shots, which were lovely but didn't move the story along.
The director's cut is still kinda languid, and it's still got a lot of gorgeous long special effects shots that won't look nearly so impressive 40 years later on a TV screen rather than a movie screen. (Even though some TV screens have gotten pretty big in the last decade.)
The cut is definitely better. It fleshes out some of its side stories, and it moves better. The effects should look pretty nice in 4K: it's all analog stuff that should scale well. And being analog they hold up surprisingly well (where CGI usually seems to feel awkward in just a few years).
The DC is a lot more watchable. The biggest benefit is the CG Sequences, which are used to replace some of the 'staring at the viewscreen' type reaction shots.
As for why it wasn't remastered at 4k, let alone 1080p back then, my guess is that the cost of rendering CG above DVD resolutions was a major factor.
Readit News
I saw the original version in theaters and loved it, probably because I was was a kid and so happy Star Trek was back.
Watching it years later I finally understood that it could have been better
The director's cut is still kinda languid, and it's still got a lot of gorgeous long special effects shots that won't look nearly so impressive 40 years later on a TV screen rather than a movie screen. (Even though some TV screens have gotten pretty big in the last decade.)
The cut is definitely better. It fleshes out some of its side stories, and it moves better. The effects should look pretty nice in 4K: it's all analog stuff that should scale well. And being analog they hold up surprisingly well (where CGI usually seems to feel awkward in just a few years).
As for why it wasn't remastered at 4k, let alone 1080p back then, my guess is that the cost of rendering CG above DVD resolutions was a major factor.