Voyager was likely shot on 16 mm film to start and then 1080 digital toward its end, its likely enterprise was always shot on digital but I’m really just assuming. The magic of 35 mm (and even 16) is that if the negatives still exist they can be scanned to 4k (annd probably beyond) and look amazing. If a source media is a 1080 digital file…that’s all ya got (unless you want some extra ai ears on your Mr. Tuvok.
Case in point - see the Firefly bluray transfer. I think they took the format name literally because the black levels in some scenes got raised to the point that there's just this blue haze in parts of the scene.
That’s just the work of hands of blue
Klingons also looked better in 1966.
?
Star Trek TOS was filmed in full 35mm film. Voyager and ENT were filled in much lower quality film (straight to VHS essentially). The posted images are full quality stills taken from each show (available at trekcore.com).
I thought the retina burning white square meant something.
Honestly, ENT looks pretty good. I mean, not as good as TOS remaster, but being done natively in 720p (and even 1080 in later seasons), it doesn't look that bad.
Get the VERTAG upscale if you can.