i wish we had paramount still making trek then wed have 24ep seasons again and one off episodes per week. The sale to cbs was the worst thing to happen to trek.
People wanting 20+ episodes a year of an hour long sci fi series would probably be complaining a lot about the number of those episodes that would be below par, feature mainly secondary characters and be mainly set in one or two locations or possibly the dodgy "arid planet with a red sun" or the "forest planet with the blue tinged conifers"
As has been said one of the reasons you're not seeing as many 20+ episode series these days is that to do so usually requires multiple complete production crews, large casts and people to be routinely working 12-18 hours a day for months, with things like props and sets suffering from the fact that if you've only got a few days to build and prep them you tend not to be able to do a job that stands up to modern expectations*.
American TV primarily used to do 20+ episode runs as it made it easier to sell advertising and fill a schedule for ~6 months, it was almost always at the expense of the cast/crew and a big reason why many actors would want to leave after a while as you can only do it so long without serious health issues (mental/physical), or family issues (people wanting to spend at least a couple of hours a day with their kids).
Fortunately they've realised they can tell a story with ~12 episodes, maintain a higher quality (even just allowing more time for post production), and keep a wider range of cast and crew for longer because it's something that allows for them to have some life off set, or do other things to avoid burning out.
Also didn't Paramount practically kill off Trek with their nonsense through Voyager and Enterprise...
*Most TV props until the advent of HD have a tendency to look fairly poor in person, despite the miracles that the SFX and props people would perform often in extremely limited time frames, behind the scenes books are often fun for learning about that sort of thing, I've got one that describes how for one sci fi show they needed more of the guns for a scene and basically had a lunch break to get several done as they discovered they were missing a couple and IIRC some others were too damaged to show at close range (but had been ok for background shots so hadn't been fixed as they were low priority).
