It's not because of that. It's because of how the mods work right now. For example most of the mods atm are heavily relied on scripts. With CK around mods will probably be of less size, and way more simple to make in CK.
Actually, plugins made now are generally smaller. It's changing data on a more base level. Ofc, all plugins should be fairly small because scripts aren't kept inside them, besides plugins editing cells/worldspaces.
Everything besides scripting can be done now, though actual worldspace and cell editing can be done much easier. No reason that a mod made now is going to be worse than a mod made with the CK, though.
I don't understand why people think the CK magically makes everything better *shrug* My realistic lighting improvements can only come from the java program, the actual plugin's just how it should be.