I'm in the banking API space. Yes, the current technology is decrepit and garbage. It's not the bottleneck though. Risk management and underwriting is. If you want to build a SaaS in this space, the hard part is figuring out how to vet customers cheaply and quickly. Every customer you sign up is a potential OFAC (Office of Foreign Access Control), BSA (Banking Secrecy Act), or AML (Anti-Money Laundering) violation.