I sorta disagree.
1. The civilization isn't really much of a civilization. There was a cave which they sorta used for a throne and there was an axe which a normal monkey will be able to make in a few years (they are already use rocks to help themselves out and learned to use money)
2. Kong didn't make that civilization
3. Kong has shown less capability of communication than the gorilla Koko who actual spoke full sentences while the most kong has shown is him saying Home.
You have to understand that average is a lot more serious than monkey level intelligence. That guy at the meat shop who cuts beef for a living who knows how to read, calculate, speculate, talk and knows and remembers many concepts and realities, that is the average guy.
Heck, we are actually generous to kong, apparently chimps fall under high-animalistic despite being capable of very basic communication.
Kong should stay at below average.
There is a higher chance to upgrade godzilla to below average than upgrading kong to average. Godzilla has shown both instinct and understanding of what he does, being like a raging king who has to put his subordinates in place. He knows that humans are of no harm to him and only causes destruction on his path to destroying mechagodzilla. He has shown emotion, laughing at kong running away from him, showing smaller yet similar levels of intelligence to kong. He also clearly communicates with other titans, even with kong.
Now of course, i want him to stay at high-animalistic because that is not enough, but i used this just to prove that that is closer to reality than kong being average.
If he is average then show me him reading a book. Because that is what an average person should do. If Kong is average then they should take those 5 year olds screaming on the floor above me and make them get a job, that are the intelligence levels necessary.