i think i agree
there are so many different types of books and styles out there, but for the type we're talking about, especially these characters like babar or madeline, etc. it definitely enhances the story, especially when the illustrations were created at the same time (or nearly) as the story.
conversely, i think other stories work better without illustrations... things like fairy tales or legends. they seem to be very open for interpretation and mysticism that i think illustrations could counteract that creative thought process and make them a bit less magical.
not sure if i've made sense here...