The job runs on legacy PHP and jQuery. I spent two years learning React. Did I waste my time?

Took the first offer I got, which I don't regret, but the codebase is nothing like what I studied. No React, no TypeScript, just a huge old PHP monolith and jQuery sprinkled everywhere. Half my mental energy goes into "why does this even work."

I keep worrying my React skills are rusting while I wrangle code from 2014. Anyone been here? Does the modern stuff come back fast when you switch jobs later, or should I be grinding side projects to keep it fresh? Trying not to spiral.