I realize this is a joke, but regardless these days you basically need to spend ~25% of each year rewriting your app just to stay in security compliance.
It's less an issue of our code, and more an issue of third-party APIs from our partners getting deprecated. And Angularjs, where upgrading to angular or rewriting in react doesn't really do anything for end users, but if we want to keep showing up in search results then the writing is on the wall.