Genre fandom does have a disappointingly short attention span sometimes. The TrekBBS thread for the first season of Superman & Lois, for example, is 88 pages long. The thread for the most recent season, the show's third, tops out at a mere 30 pages -- despite the fact that, by most accounts, the third season was every bit as good as the first, if not better.
There's a lot of content out there these days, so people have a lot of options and a lot of new things to explore. I guess for some folks, the shiny new object is always going to be more interesting than the familiar old one. Personally, I'm more of a loyalist, and gratefully stay with the things I love for as long as they're there to enjoy.
There are some genre shows I've been 10-20 years late in finding. I got into Merlin in November 2022 due to running across a screenshot of Eoin Macken (Gwaine) and being shocked because of how closely he resembles a character in the prose adaptation I've been doing of a computer game called King's Heir: Rise to the Throne. I'd been browsing Pinterest, looking for pictures of people, clothing, objects, etc. for inspiration, and suddenly up came this picture of someone who could have played the part of the main character in that game, if it were ever to be filmed using live people.
So of course I was curious, and the comments stated the character's name and the name of the series. Season 1 was available on Amazon in Canada, and so I ended up giving myself the 5-series set plus an all-regions DVD player for Christmas, to see the rest of it.
I've now seen most of the series at least twice, I've seen loads of clips on YT, and took a deep dive into the fanfiction. I'm now working on my own Merlin fanfiction. It's nice that at least there are still people around to discuss it on AO3 (Archive Of Our Own). The fanfiction ranges from not-great to fantastic, humor to far better than the show gave us, and I've really been enjoying it.
And yes, I wasn't pleased with the ending. Holy crap, they basically went Hamlet on the characters. So I appreciate the fanfic that people write to fix that.
I really enjoyed S&L, but I just ended up losing track of it after one of the mid season breaks. Those tend to get me, because I won't realize they've come back, and if I'm not signed up for the streaming service they're on, then I only have a few weeks to get caught up while the episodes are on the website/app, and a lot of the time they're already gone by the time I go to watch them.
I think it's pretty normal for shows to bleed off viewers as the go on. Some shows might get a boost here or there, but even then tend to start dropping back off pretty quickly.
I was a huge fan of Merlin for most of it's run, but I ended up losing track of it after a while. I think it was basically similar to what happened with S&L where it didn't realize it had come back on for the last season or somewhere later, and by time I found it was too late to get caught up. I think did eventually watch the rest of on Netlfix.
I don't have Netflix, but have found that the series is still being shown on Tubi. It's more convenient for me at the moment to just watch on that site, when I want to check something for my stories.
That's why shows get canceled eventually...
In the case of Merlin though I was looking as I couldn't remember and it seems here in the US at least that it started on NBC but then ended up on Syfy after the first or second season. It's really unclear when it comes to the final seasons but I remember it being on BBC America at some point but I'm not sure if that was exclusively so. So there's that and then for the third season it came on after WWE wrestling when that was a thing on Syfy. So I don't think any of those did any favors to keeping up an active discourse for the show.
It's so annoying when a show is hard to find. That's why it took me years to finally watch the entire Highlander series. I never got to see the first season until the whole thing turned up on the Space Channel (what Canada had before it became the vastly inferior CTV Sci-fi).
When I mentioned getting into the show on my gaming forum, half a dozen people immediately told me, "You're gonna hate the ending." They're right. I hate the ending. But that's what fanfiction is for - fix the ending and take the characters in other directions. One of my projects is a rather ambitious crossover between Merlin and Highlander. At some point Downton Abbey is going to turn up as well. It may sound like an odd mixture, but it gives me a good reason to do loads of historical research, and I'm having a blast.