Stripe, N26, SBV, Square, Brex, Monza... and many others all compete directly with banks.
That’s also very tangential to the fact that while some areas of banking, finance or weapons dealing may be dominated by large institutions, there’s plenty of other areas that are not. Stripe is a perfect example in how they started out by capturing a retail market that was outside the core business of the large players. Nobody would look at their value prop and say “finance is overfunded”, because that ignores what area they were actually trying to compete in.
If you wanted to make a startup that looked to innovate retail weapons trade, then no investor is going to tell you “you’ll never compete with Raytheon”, because no matter how big they are, they don’t compete in retail weapons trade. What they would more likely tell you is something like “we don’t invest in that vice industry”.
Make a consumer product banks can copy and try to prove its viable and I think you'll get that feedback.