Actually, characters with infinites are one of the few times that game theory can greatly influence the outcome of your match. I won't give a super in-depth explanation of what game theory is, but I can tell you that it's basically using advanced strategy, to affect anything from the outcome of rock-paper-scissors, to what job your boss might assign you.
One of the things in game theory, is that one way to achieve a favorable outcome is to limit your options. Yes, limit your options. I know this doesn't sound like much help, but what will a Dedede do when your on the ground? He will infinite you. He will try to grab you. So, all you have to do is anticipate that. Memorize D3's grabbing range, roll dodge behind him the moment he tries to grab and punish him for it. By limiting your options, most D3's will assume you're stupid and will fall for an obvious trick.
And that's why I've only been CG'd by D3's who already know my strategy against them.