It is all of that and more. James helps us also to understand:
"But the tongue can no man tame; it is an unruly evil, full of deadly poison.
Therewith bless we God, even the Father; and therewith curse we men, which are made after the similitude of God.
Out of the same mouth proceedeth blessing and cursing. My brethren, these things ought not so to be." James 3:8-10
It "ought not so to be", but so often it is. So long as our carnal mind works and our carnal tongue, they will seek to speak out those curses... and therefore when we are quenching the Holy Spirit in us they can be successful.
Throughout the scripture[both OT and NT] there are types and shadows. Of course, they have had and have their purposes, but the real things of God are what we are seeking, or at least should be seeking. As we move from seeing through a glass darkly toward seeing face to face then...
"... but whether there be prophecies, they shall fail; whether there be tongues, they shall cease; whether there be knowledge, it shall vanish away. I Cor 13:8
Yes, the types and shadows a tongues and of parables will be gone for they will no longer be necessary. We will then no longer see "men as trees walking" but rather "clearly".
You may be correct to question and doubt but casting something away while your vision remains as "through a glass darkly" could be a dangerous thing to do. They will cease in God's time rather than in yours or mine.
There is without a doubt quite a bit of babble among tongue talkers which you call "gibberish", but often it is simply baby talk as is the babble of carnal babies without regard to the carnal language of their parents. Newborns will speak that way. If the spiritual newborn never moves from babbling to speaking a language, there is a problem as there would be with a carnal child who moves up to 10 and 15 and greater ages without ever learning to communicate.
And so based on the idle words of this person and that one, you have rejected the whole thing without thoroughly checking with the scriptures and more importantly with God?
"But I say unto you, That every idle word that men shall speak, they shall give account thereof in the day of judgment." Matt 12:36
Of course none of your words are ever idle.
Your above explanation would be included in God's purpose, but why is that you seemingly presume that there is nothing you do not understand? I believe that I understand some things about the things of God, but I fall very short in very many things. He is simply too great to put into a box.
I am glad that you understand it all so well. Thank you for your explanations.
"For my thoughts are not your thoughts, neither are your ways my ways, saith the LORD.
For as the heavens are higher than the earth, so are my ways higher than your ways, and my thoughts than your thoughts." Isaiah 55:8-9