Thankfully The Walking Dead had already started declining in quality before I ever started it. Been meaning to, but just never have. Probably unlikely I ever will at this point.
DS9 was, I believe, the first real "serialized" Trek aside from the occasional two-parters. You can watch it out of order for the first couple of seasons, but after the Dominion War plot picks up, yeah, you gotta watch them in order. Luckily I didn't see any of the TNG-era Trek until COVID so got to binge them in order as the gods wormhole aliens intended.
I'm the opposite. I loved ENT. Kinda had some heavy-handed post-9/11 plots which are really hard to watch today, but otherwise I liked the "how we got from there to here" and seeing the Trek Tech we take for granted either not exist yet or be highly experimental and dangerous. I get why people don't like it, but I can look past that easily enough. Plus, the last season is basically one long TOS love letter.
SG and Battlestar are both on my "will watch when I have time" list that's ever growing.
Good luck with the Expanse. Hope you enjoy it. There's a LOT happening in the first season, so you really gotta pay attention to the factions and locations. They don't really spell a lot of things out for you other than a short intro in the first episode. I just did my 3rd watch of it recently and picked up all kinds of details I never even came close to catching on my first watch.

