It's hinted at here, but film produces a much better overall look than digital. It is just that digital is way cheaper and easier to work with. There is certainly more versatility in what you can create in post production with digital but the base look of what is captured is more beautiful on film, and this is the same with photographs. Look at high quality old images captured on film, they blow most digital images o…
Star Trek The Next Generation was famously shot on film. The HD scans are so good that the props can be seen to be fake in many places. Later franchise shows that were shot in digital simply cannot be released in HD as there is no HD source material.
This is a persistent myth, but false. DS9 and Voyager were shot on film, like TNG and TOS. TOS was also edited on film, TNG and later were scanned and edited on videotape. This makes it much more work to remaster TNG and later shows for HD, which was done for TNG but not later shows because the TNG sales plus the perception that the other shows wwre less popular and would sell less made it not worthwhile from a business perspective.