Developers want to improve their project. If you find an issue, bring it up. If it's a valid concern, the author will probably want to have it fixed. In many cases, the author will consider it a valid issue, but simply not have the personal time or need to address it immediately. This is where open-source is great. Just fork the project and fix it

I don't believe the sprockets and sprockets-rails maintainers (actually it's up to the Rails maintainers, see rails/rails#28430) currently consider it broken. (I am not a committer/maintainer on any of those projects). So there is no point in "waiting for someone else to fix" it; that is not going to happen (unless you can change their minds). You just need to figure out the right way to use sprockets 4 with rails as it is.