Frameworks give a good knee up but not enough to make programmers interchangeable with no investment in learning A 2-decade old project probably would take suc

Frameworks give a good knee up but not enough to make programmers interchangeable with no investment in learning A 2-decade old project probably would take such a long time to re-write into a modern framework that the time would be better spent investing in devs willing to work with your system Particularly in JS, you may find after the re-write your framework of choice moves on without you and you're back to square one (though this is slowly stabilizing) Obviously, there are exceptions, maybe the new language has persistent data structures or strong concurrency primitives that would be difficult to home grow that should move the needle of your decision making, in which case you may want to use new tech at the edges of your system, but you'll need to make peace with the fact you'll likely never finish the full migration and it will complicate onboarding, ultimately this should align with the personality of your team I think