Overview
Your app still works. That is exactly why it gets neglected.
An application that quietly does its job is easy to leave alone. Then a few years pass, the Ruby and Rails versions it depends on stop receiving security fixes, hosting providers retire the old stack, and every small change takes longer than it should because nothing around it is current.
Upgrading is the most reliable way out, and it is one of the things we do most often. We have maintained and modernized Rails applications for well over a decade, including a client application we first built in 2012 and most recently brought up to Rails 8 on Ruby 4.
We upgrade in small, tested steps, one version at a time, so your team keeps working the whole way through and there is never a risky all-at-once cutover.