Well for the story to work, there had to be some reason for vengeance. And Fillion had scheduling conflicts so it got to be him.
Was it done particularly well? Not especially. They had to suddenly backjam a giant pile of off-screen story for both Cayde and Uldren in that felt kind of inorganic. Nevermind the whole "Maybe you're a murderer" trackline while literally forcing your hand (and ignoring the dozens of sentient capable of reasoning aliens we killed on a standard basis.).
Repercussion wise. Its also a little soft. Maybe if our new super had arrived post-storyline (or mid-storyline from a different source) that could be worked in, as us embracing a path outside of the Vanguard's rules. Thats kind of where it really falls flat. "Hero" characters who go renegade like that become labelled as loose cannon,s imprisoned, or let go until the next crisis is dire enough. Ours just wanders back in and takes up regular old day to day Vanguard life with barely a sentence from anyone about it.
I thought North actually did a better job than Filion because he seemed like he was loving the role. So much more life and energy into the character. Thus it wasn't necessary. And a revenge story isn't always the best idea.
This is how the story could have been much better not perfect nothing is because I think his death was very unnecessary.
https://www.bungie.net/en/Forums/Post/248744912?showBanned=0&path=0
Most of that would be less rushed yeah. I'd have put Cayde's actual death confronting Uldren at the crystal on Earth (the cutscene where Petra is inexplicably there and misses him with the sniper. And then escapes seemingly unscathed, Uldren clearly doesn't care, and she doesn't bother telling us about it so IDK why she was there at all from a storytelling standpoint). Since Uldren mucking about with a Traveller Shard would draw attention (again something that just kind of floats by unfollowed on), that leads the Vanguard to find Cayde's body.
Some of it could also have been made a bit more organic if they'd had a mission or event to capture one or more Barons leading up to Forsaken. Rather then plonking down 8 supposedly legendary dangerous antagonists out of nowhere.
As it stands, you just get the (probably after the storyline) exposition dump from the lore bits to explain why Uldren is suddenly a full on bad guy and any personal rivalry he has with Cayde and that Cayde was seemingly at random running around helping the Awoken collect prisoners after the Red War (when we're the ones that Petra was in regular working contact with before)