"They claimed to want to start open sourcing large parts of their tech from 2023 onwards."

I work for a different financial company that said something similar about contributing to open source. That was 10 years ago and still nothing. So take this skeptically.

"Politics is everywhere, people will fight you not on technical merit but because they want to claim responsibility for something even if its inferior to the product you could build - if you don't have the support to push through this I suspect you'd get stuck here.

Corporate structure is confusing because everyone's titles are massively inflated."

This is also true at my company.