For a large project with dedicated resources that is pretty reasonable. And GitHub issues probably isn't sophisticated enough for you anyway. But for a small to medium open source project, that's a lot to set up and manage, and in the case of gerrit, you have to host it yourself.

And then for Youtrack, Jira, Confluence, etc. You still have the same problem where it is difficult to migrate to a different system, because the data is all stored in a proprietary format that can't easily be ported to something else. For the wiki, there are somewhat standard formats used by multiple systems, like markdown and mediawiki. But for issues, I don't know of any standardized format, and migrating from one product to another is going to be pretty difficult.