We should pray in secret to our Heavenly Father. But there's really nothing wrong with praying 'with' a group of believers either.
But what you're talking about is their idea of 'praying in tongues', which would mean that you agree with that per 'their' view. Thing is, their view of what 'praying in tongues' is, is not Biblical. Apostle Paul taught no such idea.
When Paul spoke of someone coming into the Church with a "unknown tongue", he was pointing to known languages of the world. Simply, if someone who only spoke Chinese came into the Church and there was no one to interpret, Paul said for that to keep silent.
And by the way, the word "unknown" in the KJV phrase "unknown tongue" in 1 Corinthians 14, IS NOT WRITTEN IN THE GREEK NEW TESTAMENT. The KJV translators ADDED that word "unknown". The word in the Greek there is simply Greek glossa, which means a known language of the world.
And that is the MAJOR HINGE POINT of properly understanding about the cloven tongue of Pentecost. When it went out, it went out as KNOWN LANGUAGES OF THE WORLD, even in the DIALECTS of the towns where those present were born. It was NOT gibberish speech, which is how many are fooled into thinking that gibberish talk is the true cloven tongue. The TRUE cloven tongue per ACTS 2 was UNDERSTOOD by everyone present!