In my case, I'm generally a mix of full stack dev and game dev (specialised in HTML5 game dev). I want to do more systems stuff (particularly Rust), and I've recently created a scripting language with a VM from scratch for a game engine as part of a side project.
But I don't have any commercial experience or keywords for recruiters to find in my CV outside of what I'm already "expert" in, and it's hard to find companies that will understand that a good programmer can transfer skills from one language to another.
To give an example, I recently got rejected at one job at the CV stage for "not having enough React experience" because my last job was in Vue so I wasn't technically using React in recent years (even though it's an extremely similar area of expertise)