Skills are quite interoperable, and you can easily ask Codex / Claude to help you with switching the MCP connectors or any other things specific to your previous workflow. It's been quite low friction in my experience.
It strikes me as like setting up an IDE. People have preferences, switching is possible, but there are advantages to saying "we are a Visual Studio + Resharper shop" or "everyone uses IntelliJ to work on this project".
You install MCP connectors, specific skills, work around model/harness quirks, set security boundaries etc.
It's a lot of work, and most people will never want to change it once they have it working.