I'd bet the typical payments integration has more complex requirements now than those from 10 years ago. That's what usually happens as a space becomes more important and, therefore, more regulated. Usually new entrants will come in and try to provide a tidier interface for solving an increasingly complex problem. In payments, as others in the comments have pointed out, that process is hampered by the gatekeepers involved.

You'd have to commit to building an amazing developer experience and navigating bank partnerships and compliance (per country), risk, antifraud, etc.

That's why the payments devex feels so behind the DB, hosting, or auth devex today.