All the languages and libraries you've listed are open-source projects started by someone like yourself.
> "having done every type of CRUD under the sun - what do now"
You have a lot of experience developing CRUD, why not build something that alleviates the pain of CRUDdy development. What annoys you? What sucks and could be done better?
Anyway, just a thought. Good luck to whatever you do.
I'm far from being good enough to contribute to open-source projects unfortunately. I can make lots of things work but I don't know enough advanced patterns and low-level stuff to contribute in a meaningful and maintainable way.
You could start by triaging issues, something that is very tedious for maintainers, especially on small projects. More than that, you can look at each issue and try to see if you can identify the problems. You may find you are better than you think.
There isn't a level you need to be to contribute - it may feel like that because on higher profile projects most of the low hanging fruit has already been addressed.
Beyond that, there's a skill you learn here - practice communicating professionally (sometime people are submitting issues when they are extremely frustrated), concisely, and clearly (sometimes you need to speak highly technically, other times speaking with a management voice is needed)
In the same vein, there's plenty of poorly documented READMEs and wikis, other areas you can contribute, and skills that are very important.
Strong communication and writing skills can level you up over better developers.
I think the barrier to contributing to open-source is far lower than you imagine. There is, for example "good first issue" tag on many repositories (search Google for terms like "awesome for beginners" etc).
One example, I recently contributed to chokidar - something that is used by webpack, VS code, etc - fixing a bug that prevented network path access, and all it took was a conditional statement to handle the edge case: https://github.com/paulmillr/chokidar/pull/1025
The barrier to entry of open-source is far lower than you think (I'm proof of that!)
Most great projects that have advanced patterns evolved from simple toy projects. They only became advanced with the collaboration and help from internet strangers ;)
If you're looking for a project that is amazing and could use some love I recommend librivox. I think your skills would be great for helping them. They recently put out an ask here: https://news.ycombinator.com/item?id=23558686
Find a project that you like, and want to support. You could write a blog post about this, a guide, a historical review of the project, a list of people/companies using it. etc.
Most open-source projects need communication attention more than programming work.
You will do a great helping giving attention to an opensource project.
This. I think it's pretty good practice to check out what's going on under the hood in libraries you use, or plan to. Sometimes you find interesting libraries or techiques, things you could improve and in rare instances that you need to stop using it...
All the languages and libraries you've listed are open-source projects started by someone like yourself.
> "having done every type of CRUD under the sun - what do now"
You have a lot of experience developing CRUD, why not build something that alleviates the pain of CRUDdy development. What annoys you? What sucks and could be done better?
Anyway, just a thought. Good luck to whatever you do.
[1] https://i.imgur.com/qr7Sr8B.png