You'll find that knowing different systems helps your career. Every new bootcamp grad knows React. You can learn React on your own, and know React + Outsystems, making you more unique.

It is counter-intuitive, but knowing non-trendy platforms makes you more valuable. When projects come up needing to integrate with the newer platforms, or if they drop Outsystems to move to node/React, you would be one of the few people who know both sides.

I've spent most of my career on platform transition projects, migrating Lotus Notes to .NET and SharePoint, and building web front-ends over them to replace their old UIs. Now, I am modernizing older .NET MVC and jQuery apps to React running in cloud environments. The tech list I work with would make most people run away screaming, yet I'm extremely valuable to my team because I know every piece of tech on both the old and the new platforms.