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.
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'm a self taught developer from the late 90s)
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
Most great projects that have advanced patterns evolved from simple toy projects. They only became advanced with the collaboration and help from internet strangers ;)
Most open-source projects need communication attention more than programming work.
You will do a great helping giving attention to an opensource project.