Citi (and most financial services companies) is very careful about what goes into production. Engineering processes are taken very seriously. That can be a valuable learning experience. On the flip side Citi is largely process driven and doesn't do "Move fast and break things", which I often wished Citi did.
As an addendum some software engineering teams also do/work with cutting edge quantitative finance research work which can be interesting and lucrative. But that totally depends on the team you join.