I feel that the user is coming from a place of wanting to gather experience and show it, and read somewhere that open source is great for this. But lots of projects are open source not to favor external contributions, but for other reasons. And external contributors will typically be long term users of the software, who already have deep knowledge about it and a personal interest in moving it forward.
If the aim is to get experience, I am actually convinced that it is easier to get an entry-level job than to invest the time and effort to be able to make significant contributions to big open source projects. Of course if you manage to get a job where you can contribute to open source, even better.
Good luck!
Is it to build a personal portfolio of contributions?
Would you eventually like someone to pay you to contribute to the project