Yep. Just today I was working on a project that I started as a simple set of forms with HTML, CSS, and light vanilla JS + jQuery which over time has naturally accreted a bespoke event-handler framework (really not a bad one, all things considered), wishing I had just done it in React from day 1. Now we are battling complexity every day to support a highly interactive app and we're going to have to try convince the client to give us some time to refactor for some breathing room.