Well you're claim is not correct. Let's be accurate about this. What I've contended is that every example that I have heard and every example that I have encountered in video and audio recordings is gibberish and not a language with structure, syntax, and vocabulary. And the examples on youtube, in my local Pentecostal assemblies, and probably in those near you do in fact turn out to be gibberish when checked. It is not as if there are credible verified examples of people speaking in tongues today that turn out upon close and careful examination to be Cantonese, Greek, Swahili, Italian, Afrikaans, or some other language that can be translated and whose message can be verified. And what is particularly telling about the whole Charismatic enterprise and its manufactured miracles and fake gifts is that when they are checked and shown to be gibberish or fake healing etcetera then the advocates claim that there are some bad apples in the barrel and that one 'ought not to throw the baby out with the bathwater'. Some of the most scholarly advocates say that tongues is an angelic language that does not conform to earthly linguistic norms; how convenient that is, it sounds like what a confidence trickster would say when his/her game is discovered to be a trick.
The basis of my judgement is godly discernment. The holy scriptures warn against lying wonders and the holy scriptures tell the faithful that 'by their fruits shall ye know them'. Well, the fruits of many of the prominent televangelists are what exactly? Wealth, mansions, Lear jets, excess, moral failures, and a host of other negative things.
And what do I personally believe in? it doesn't matter very much but I do believe in miracles and I do think that people receive visions and messages from God today yet those who receive these things are not wealthy televangelists who worry more about the size of the donations they receive than about the grace given to the humble and needy.