Um, this is weird - which "senior" designers did you talk to? This technology definitely exists, there are already companies/products out there tackling this problem such as Butter - https://www.justbutterit.ca/ and they use fintech aggregator APIs like Flinks or Plaid. The technology definitely exists, these "senior" designers need to be checked, because that's just ridiculous. I'd say your big failure was also not doing a competitive analysis and/or checking in with senior developers.