> Is the error handling issue serious enough to stop developers from even considering Go

If it is, then I suspect those developers are going to have a thousand other non-overlapping reasons not to consider Go. It seems like a colossal waste of time to court these people compared with optimizing Go for the folks who already are using it or who reasonably might actually use it (for example, people who would really like to use Go, but it doesn't support their platform, or it doesn't meet some compliance criteria, or etc).

If you shake things up so much that users who previous dismissed your language are interested, you might also be making a big enough change that your current users look around as well. The pool of prospective new language users is always large but they won’t join a language that is dying because it churned all its existing users and package maintainers.

I say this as someone that gets a very bad taste in my mouth when handling errors in go but use it a fair bit nonetheless.

If you're writing the universe, maybe. There aren't that many competitors when you take the ecosystem into consideration. It is the only reason I tolerate Go where it makes (some) sense — mostly CLI utilities that are too complicated for bash.

Every language has the potential to attract new developers if they change/add just this one thing.