In my experience it unfortunately often hasn't been a net benefit for the projects I worked on. A "good first issues" takes up a lot of time to write and often never get addressed at all or it takes even more time to review and give feedback ultimately causing more work than addressing it directly since most "first issue" contributors do not come back to contribute again.
GitHub has done a lot to streamline the process of contributing to an open source project. I think what is still missing (or I don't know about) is an overall resource where you can learn about open source best practises (or just "Best Practises" since you should be using them everywhere) like writing tests, writing good docs, using conventional commits etc. outside of individual projects - and then in addition to the "Good first issue" label also indicate which one of those best practises apply to that issue, e.g. "This is a good first issue if you know about NodeJS, Mocha tests and Markdown".