You mentioned in your OP that it would take years to create a hobby project worthy of attention from a recruiter. I don't think this is true. If you spend some time learning ES6/React/Redux, for example, you can "string together" a few libraries/APIs and create an impressive-looking application in a couple weeks or so.

For example, I made this little application in a single day (sorry for plug, I just wanted to give a concrete example -- I'm not gaining anything here). I just accessed the crates.io API for my data, paired it with a D3 module wrapped in a React component, stylized it, and added a search field. It's a really small amount of code, plus I didn't have to set up a a database or even a server (hosted on github pages). Yet I now have some "proof" that I know (at least the basics of) this particular tech stack (my "primary" field is embedded/application development).

Lots of recruiters noticed this project on my LinkedIn and asked about it, so it was a worthwhile investment for sure. I've done similar things with other tech stacks to get past the overly discriminating recruiter firewall.

It takes a little creativity, but you don't have to slave away for years on a moonlighting project to prove you're capable with a set of technologies.