Question: Why G-d had to confuse people's languages in the land of Shinar and scatter them across the Earth with diverse languages? What moral does Genesis 11:5–8 coveny to mankind execept the fact that "in order to initate a huge project and achieve its result, there should be no communication gap". And if this was good then why God scattered them?

It seems that Genesis 11:5–8 is revealing as if God was helpless and was left with only one option i.e. confusing people's tongue and not letting them understand each other.
Had there been just one language, may it be Hebrew or Arabic or any other language mankind used to speak then mankind would have been living peacefully and prosperously.
Why would it be not acceptable to God?

Please explain with clarity. Thanks

Answer: 
Ralbag suggests a fascinating approach to understanding the incident. He explains that
these people did not sin in any way. They were not dispersed as a punishment. Instead, they
were dispersed in order to assure the preservation of humanity. Concentration of the entire
human race in a single location created the possibility of sudden extinction. A localized natural
disaster could destroy the entire species. Through dispersing humanity the impact of a localized
natural disaster was diminished. Should a specific location experience a devastating disaster,
only a portion of humanity would be destroyed. The remainder would survive.
Ralbag makes another important point. He discusses the manner in which the Dispersion was
brought about. Hashem awakened in families the desire to differentiate themselves. This led to
the establishment of different customs and eventually completely unique languages.

See רלבג עה"ת ספר בראשית פרק יא פסוקים ב-ט
I believe that what these people were after is to "build a name for them selves" apart from God, or as someone here said, in defiance of Him.

So the question is not if God was helpless, the point is that they were alienated, as godless men ever since Adam's sin are, and as such they commited to "reach the sky".

And since even the ability to communicate in unity & harmony is really a blessing
from God, He did not need to do anything agressive to disperse them.

He simply withdrew His own blessing, which is inherent to Him and to those He favours.

Because He wishes to bestow blessings thru communion with Him, 
not outside of it.