React or Vue might be around in 15 years, but they'll certainly look vastly different. So unless you have a continues budget to stay up-to-date, with room for the occasional rewrite, your developers will be stuck on "old tech" in a few years.
This may not be a web application, if not: WinForms. WinForms will survive another decade or two and will get no new features so it's a stable development platform.