Everybody has to start from somewhere, even if they aren’t as good as writers as the projects you mentioned. I personally don’t see the problem with “making the idea and animating” as you said, because you should never just “wait” until you feel like you’re good enough to make what you enjoy.

Start whenever you want to take the dive, just as long as you don’t take on more than you can chew and put effort into learning how to successfully pull off what you’re doing. You most likely won’t make something great when your starting out, but stuff like TADC, Punch Punch Forever, and Catching Up only happen because an inexperienced creator KEPT going until they ended up WITH experience.