You don't need to vibe code an alternative to excel, you need to vibe code a solution to the problem you're solving with an excel sheet.
Any nontrivial excel sheet should be a database backed application, the finance guys who build them are in every sense programmers they're just using the wrong tool by convention.
You're missing the point that the users don't want an application. They want to go off on flights of fancy altering the "solution" as they see fit. Excel lets them do whatever crazy thing they want without constraints. Having a database-backed application is exactly what they don't want because they can't be "creative" with it.
I agree with you, BTW, but I've never seen moving Excel sheets to an application work in practice. You can do it, and it just creates more Excel sheets.
An agent, sqite, and some html. Are what they want.