It already is an issue and it works both ways. Engineers going to companies with proprietary stacks need to spend a lot of time onboarding. And engineers moving

It already is an issue and it works both ways. Engineers going to companies with proprietary stacks need to spend a lot of time onboarding. And engineers moving out of companies with proprietary stacks need to reorient themselves to the open source tooling. But to a certain extent, that's part of the job description. If you move from a company that uses RoR stack to one that uses GraphQL or Node, you're going to have to learn the ropes.