The only other tv I've rewatched as many times as an adult is Poirot - with Star Trek it's considerably more for a very few episodes but once only for others (much more variable quality for Star Trek than Poirot - though the latter also had quite a collection of different writers, directors, and producers, and even switched owners midway through its 25-year run). It feels to me like even the best episodes of Star Trek are pulpy enough to hover around the worst episodes of Poirot for rewatchability, even though as bad examples of their genre the worst Poirots are definitely worse in absolute terms than the BEST Star Treks - it's just the genre and register and how my brain works I guess.
Actually, I think murder mysteries in written form are also maybe easier to read casually, with more skimming and less engagement, than science fiction adventures? As I think about it, my mom uses both mysteries and paperback romances in this way - as palate cleansers between science fiction and fantasy books, or for when she doesn't have the brainpower/attention span for serious engagement. So maybe I just copied it from her, but it really feels easier.
I suppose that reality tv also allows for that lower level of engagement, but most of the reality tv I've tried to watch has ended up putting me off for one reason or another. I still watch new seasons of RuPaul's Drag Race, although not right away, and I think the reason I've never got fed up with it as with Project Runway for example (aside from the lack of a sudden disastrous drop in quality...) has to do with how it's so camp and upfront about the amount of gimmicks involved. But it's still got a high level of hystrionic interpersonal drama for my taste (obviously, this is a draw rather than a deterrent for many people, so it's not like I censure it for this). And I think that ultimately, the whole contest aspect to a lot of reality tv puts me off: feeling bad for the losers and disliking the things producers do to try to make you like and dislike people.
Instead of that, This Old House is really a documentary and basically only shows skilled craftsmen and experts in their fields at work, doing the various things they do and explaining them as they go. I also am more interested in the care and fixing of old buildings, mechanical systems, woodwork, etc., than I am in most of the subjects of these other reality shows. A lot of house-related shows that I used to see in the US on HGTV and its forebears wasted too much time on human interest (I hate human interest as a genre: it always seems to make me way less interested in humanity in general) and featured some guy yelling in front of a bulldozer about how big things are or how extreme something is, while This Old House shows closeups of people using tools and explains what they're doing well enough that, in many cases, someone could follow their instruction to do it themselves (provided some experience with the tools and general area in question, like carpentry or masonry or plumbing, all areas that my mom, for instance, or my aunts and uncles, have experience with, even if I don't).
Another thing I hate on a lot of house-related shows are the interior design bits - I love interiors but I hate the buzzwords and jargon (a common thing to make waxjism
laugh around here is me yelling "RARGH, INTERIOR-DESIGN-SPEAK!!!") and also the over-designed results that a lot of professional interior designers on tv and in magazines seem to produce. This Old House does work with designers (and owners) with taste I don't like, but at least it's not too often, and only occupies a small part of the screentime for each project. (It helps that the host isn't an industry professional and is always there as the audience surrogate, and his attempts to sound polite and excited when I can tell he actually hates something are also a thing of beauty.)
One thing that is amusing and somewhat annoying is that the way reality tv works to create narratives that mimic fiction causes my brain to read it like fiction and start shipping people and sometimes lie awake sternly trying to talk my brain into investing its shipping energy in something with an actual fandom so I'll have something to read.