> Whatever framework you choose will be obsolete in 5 years. I am predominantly not a frontend dev, but when I do do frontend work, (and I don't avoid it by any means,) I have been using React for the past... 10 years now? And while some sentiment has been moving towards Svelte, by the time Svelte overtakes React, it will have been in production for just as long probably. And Angular might eventually run out of steam…
Are you using the same version of React that you started 10 years ago? More importantly can you use the React version that was 10 years ago ? Can you even build a 10 year project ?
As far as a React program from 2015, the maintenance required to get it working in modern React probably wouldn't be all that bad. The biggest transition in React's existence was the move from createClass to ECMAScript 2015 classes. React predates the existence of ECMAScript 2015 classes, having been released in 2013, but once they were available React 13 (2015) they were pretty quickly adopted for reasons obvious. So I'd expect a project from 10 years ago to probably still be using ECMAScript 2015 classes. If not, that transition is mostly mechanical. Definitely a few other potential compatibility breaks over the years, but they're all documented. None of them are going to require a full application rewrite.
Can you build a project from 10 years ago, using 10 year old React? Well, yeah, if you want to. You'll need to use an old version of Node.js most likely, but npm still has all of the old packages.