Well I'm in the mood for a rant about Legends of Tomorrow as well:
I hate LoT Season 1 more than the average Arrowverse viewer. Almost everyone can agree it was pretty bad but I hate it more than most, for many of these reasons. That season was an absolute dumpster fire for me, almost comparable to Arrow Season 4. It was decent at first but it got worse and worse for me.
For starters, as everyone agrees, Vandal Savage is awful. Unlike even Damien Darhk, who at least brought charisma to an otherwise inconsistent and overused character (in Arrow, not Legends), Vandal was just boring. And they never even addressed that Malcolm revived him after the tease in that year's crossover.
The plot is an incoherent mess, the inconsistency with time travel rules is at its worst because Rip is constantly yelling at everyone about how you can't break a certain rule of time, sometimes completely contradicting a previous "rule" every single episode and everything works out. It happens in later seasons but not as much, and at least then he isn't being an absolute hypocrite because in this season his entire motivation is to change time anyways.
And it only gets worst by the last few episodes. Vandal Savage is revealed to be working with the Time Masters because WHAT A TWIST and from what I can tell no other reason other than getting around the fact that they had no good motivation for not helping Rip save his family.
And that's not even the worst "twist" they attempted in the last few episodes. In the penultimate episode they have one of the dumbest things I've seen on television: "Everything we've done was mind control" or something like that. It was phrased as "controlling their fates" but it effectively boils down to the same thing.
I don't even remember what purpose that even served to the plot other than giving the Legends a MacGuiffin to destroy so they could drag the plot out one more episode, and giving Snart that cool "No strings on me" line (Which was not worth it in the slightest). Not to mention, they kill him off then too, for seemingly no other reason than to prove he's a hero. I really would've appreciated some deus ex machina save there, because I cannot think any justifiable reason to permanently kill off Snart, even if it is possible to bring him in from the past or an alternate Earth.
And then the finale was just forgettable. Something about fighting 3 Vandal Savages in different times and meteors or something (I literally do not remember what his plan was) and then, the good news, the Hawks are gone, and then your usual tease for next season which didn't do enough for me. It took a lot of persisting from the internet to get me to pick up LoT S2 and it was worth it.
I can forgive them moving over most of the characters from Flash and Arrow to Legends, other than Snart and maybe Sara (if only because I feel she shouldn't have been killed off in the first place back in Arrow S3) but the rest are fine. They're all perfect and welcome additions to Legends and I think it wouldn't be the same show without them. If they want to do Rogues on Flash they at least have the Heat Monger guy, but you can't replace Captain Cold.
The crossover is apparently his last episode as well, and it doesn't seem like the actor really wants to leave or anything, so I think the Arrowverse in general just for some reason doesn't want Snart to stick around despite him being a fan favorite and practically essential to doing a proper Rogues team-up.