Indeed Ronaldo has a poor record at major tournaments but I don't agree with the notion that Portugal are that big of a team and they would go wow without Ronaldo.
They are a bit of lucky to not have missed a single tournament in recent times when England, Italy, Netherlands have all missed some tournaments over the years. As El Professor mentioned those playoffs vs Sweden, which is one of the many times they flirted with not qualifying and Ronaldo deserves credit for bailing them out in those qualifier matches quite a few times.
If not for the expansions I'm pretty sure they would've missed some international tournaments post-Ronaldo