We are begining to see the limitations of language already, on this thread.
The point about language is that it is based on things either existing or not existing.. and even more problematically, our thinking follows our language/concepts. It can be difficult to convey more nuanced ways of existence (see I fell into 'existence' trying to convey that!). In any case that particular limitation is linked to understanding nibbana. Another problem is trying to describe transcendental states, with language used to describe mundane states- again in reference to nibbana, but experientially (the previous one was, conceptually). There is also the problem that even mundane meditative states can't be described accurately because language has been created to talk about non- meditative experiences which are mostly 'out-there'. So we use special terms (eg: samadhi) to denote them. In any case language is a poor substitue to experience because as the saying 'a picture is worth a thousand words' suggest, it is not easy to put all of what you experience in a single moment, in to words.
Importantly the first steps in to the dhamma constitutes of words and thinking- you must be able to understand someone teaching you the dhamma and have the concepts (which are derived from language) to think further about what you just heard (and hopefully understood). This is called the wisdom of hearing (sutamaya panna)
followed by the wisdom of contemplating (cintamaya panna)
. These form an important base for the later meditative practice so that you are fully aware of 1) the reasons why you are practicing 2) how to practice 3) what to expect when you practice in a certain way 4) how you know you have reached the end of your practice .. and so on.
It would be impossible to survive without language- first we must eat, drink, be stable and educated to some degree before we can practice- these serve as a foundation, even though not expressly stated. A more useful endeavour would be to bring up kids with as few defilements as possible- indeed the Buddha says that one of the duties of a parent is to teach children what is right and what is wrong (singalovada sutta).
As for self-hood, yes like all defilements, it is helpful for survival for animals- ie those creatures who are unable to think rationally and logically. This ability to think clearly, without needing defilements/ignorance to drive us to survive, find food and shelter etc, is said to exist to a degree that would make enlightenment possible, after around the age of 7 years. But of course, other animals cannot be mindful and think/plan in a wise manner, so needs to react to the environment, rather that act rationally. Now the problem with that is those more crude drivers of behaviour not only allow beings to exist, but causes them untold suffering in the same single stroke. Craving drives us to eat- but then causes heart attacks and obesity, because it becomes mindless. Similarly for all those impulses which drive us to do immoral acts for instant gratification, but cause so much unnecessary suffering. Equally the self view is helpful to a very basic degree, but exacts a very high price, for it's limited usefulness.
Hope that makes some sense,