SPOILERS FOR SAVITAR'S IDENTITY!!!!!!!!!!
Ok so I have a theory as to why 2024 Barry was so broken and why he claimed to not know Savitar's real identity.
2024 Barry isn't broken after 10 years because Iris died, he is broken because he knows that one day he will become Savitar and he will HAVE to kill Iris and the reason he wouldn't tell 2017 Barry about this is because he didn't want to cause Barry any pain as he knew it was all about to happen for him.
Also worth noting, I personally think that Iris will be saved but it will cost Barry in some form. I would love to see them kill off Iris and then have Barry time travel back just to save her.