The Flash, now that one's a tossup for me and seems divisive with fans. I liked it up to the end of season 5 but after that it just started to suck and Cecile was one of the most annoying side characters, then they gave her powers, and a sound effect. Near the end she got a tight costume too... Yeah nup
Fans seem to hate Iris West but I didn't mind her
I actually thought Iris was fine, but man the "Mirror Iris" saga was total trash. The Flash's biggest flaw was how terrible it was at Season/half season arc villains post Season 3, and all the stuff with the Mirror World was about where I finally stopped regularly watching the show. Well, that and because of the upporting cast starting to flee the ship at that point. Once we had no regular Wells and Cisco was out the door the show really hit the bottom. The fact that they thought that Chester and the reporter woman were good cast additions was just ridiculous, and what they did to Caitlyn/Killer Frost was so stupid it still boggles my mind.
They're all on either Netflix or Max, but I can't remember where the cut off is. They originally had an exclusive deal for Netflix to stream the Arrowverse series, but once (HBO) Max started all the new shows went there instead while the shows already on Netflix stayed there. I think the cut off might have been Legends, but I don't have Max or Netflix right now to check.
Max, in the US, has Batwoman and thats it for the Arrowverse. Naomi, Stargirl and Superman & Lois are all on Max and aired on the CW, but they're officially not Arrowverse shows. Everything else Arrowverse is on netflix (again, in the US).