Only one chance at end game Citadels?

Is this for real? So i can never finish the final quest because I got killed at the boss in Iron Citadel, on any character? My entire game is just ruined?? There has to be at least a rare drop that lets me try again, right? Why would I keep playing this? I dont mind hard bosses but like I should be able to try again when I dont stupidly use a 100% enemy ailment threshold for a frost build. A definitive answer would be nice, so I know if I should even keep playing this.

is this a serious post? about you just not being good enough or making a bad choice? just get better at the game and try again at a different citadel lmao..

Fyi you dont even have to do the citadels unless your SSF just buy the fragments and go to the monolith to try the arbiter fight. (which sounds like you will die there too if you cant kill a t15 boss)