Emmanuele's position seems to be that there are better alternatives to Vala, so you should use them instead; based on his tweet about LLVM-based languages, I'm guessing he is a fan of Rust. I've played with Rust a bit, and while I prefer it to JS and Python, I like Vala much better… For me, Rust isn't a better alternative, it's an worse alternative (though still better than JS or Python).
Every language has its warts. Emmanuele mentions some of Vala's big ones, but if those warts don't bother you why should you care? If you're happy with the current gdb support, what does it matter that it's not better? I may not be a typical user, but I actually prefer debugging the generated C since it gives me a better view of what is really going on. Vala isn't be seeing a lot of new feature development (especially compared to languages like Rust and JS), but it's still alive. Personally, I don't feel a great need for most of the features it's lacking, and I find it it much more pleasant than the other options for writing GNOME/GTK+ applications, so I'll continue to develop new applications in Vala where appropriate.