Yes, we know you are convinced of this brother.
But Paul did not say: to pray in the spirit is to speak in tongues.
He said: if I pray in tongues, I am praying in spirit.
His statement does not say that it is impossible to pray in spirit any other way, for instance, silently and with no words uttered at all.
Has it occurred to you that you have taken away praying in the spirit from a person who is not capable of producing speech of any sort? What about a deaf and dumb mute?