It is possible to have a view in which a grammar has some description, and a bit of prescription. If someone speaking English used only "sentences" without verbs, then a bit of prescription might be in order, and the response that "grammar is descriptive not prescriptive" would or should fall on very deaf ears. For the language at the moment does have verbs. And the same is true if someone confuses "infer" and "imply", for example. On the other hand in American English "insure" has replaced "ensure", so "insure" in US parlance now has two meanings, and one of them ("to make sure that") may be in the process of being forgotten. I find this hard to take, myself, but a descriptivist has a case here too. It is obvious that most living languages do change over the years by shifts like this one. But the basic structure of the sentence is fairly stable over a long time. I do not think that English could suffer the loss of all its verbs and remain in any reasonable sense the same language. About changes over time: Shakespeare was the first to use "ruin" as a noun, for a fallen-down building. That took some imagination and some time, from e.g. "the ruin of my house"; was the usage wrong when it came to mean "my castle falling down"? Certainly not for us; we use the word "ruin" of the stones and other materials left over from a building that has collapsed all the time, and perhaps also of the process, the ruining. 'The ruin of Widdershins Castle took place over a whole century.'
My answer is a little different from Olilver's. Why do so many scholars and intellectuals think that language is necessary for thought? Answer: Because it really is easier to think about definite rather than indefinite things. But indefinite and formless things also have to be thought about. It takes more of an effort of course to think in a pathfinding sort of a way about something new, and one may or may not be thinking "in" language, whatever that means (muttering to oneself, sub-vocally?) If one is trying to come to an understanding of some hard and new logical or mathematical matter, it may be more like shaping forms in ones mind, and then moving them, and less like chattering in French. If one insists on calling "shaping forms", or whatever the metaphor is "a kind of language", then of course the claim is drained of any content, and with that of any interest. People of say that mathematics is a language, or a "language", something like a language. But it has a function and a status very different from those of a language.