It is not. As a case in my point, Spain had a blackout last year (and I completely believe they are competent professionals - the task is just hard).
> It's just that those interconnections haven't been built yet.
They haven't been built because the grid isn't just a technical problem. It's also a socioeconomic problem, and adding new interconnections would require finding who needs to pay for it ; and currently, that question has no answer.