I have not seen any evidence of either. We have no way of knowing if we are “definitely” a true general intelligence, whether as individuals or as a civilization. If there is a concept that we are fundamentally incapable of conceptualizing, we'll never know.

On top of that, true general intelligence requires a capacity for unbounded growth. The human brain can't do that. Humanity as a civilization can technically do it, but we don't know if that's the only requirement for general intelligence.

Meanwhile, there is plenty of evidence to the contrary. Both as individuals and as a global civilization we keep running into limitations that we can't overcome. As an individual, I will never understand quantum mechanics no matter how hard I try. As a global civilization, we seem unable to organize in a way that isn't self-destructive. As a result we keep making known problems worse (e.g. climate change) or maintaining a potential for destruction (e.g. nuclear weapons). And that's only the problems that we can see and conceptualize!

I don't think true general intelligence is really a thing.

I honestly believe it is an issue of communications, and our civilization does not take the skill of effective communications seriously, so a huge amount of information lost is really the defining factor of our entire civilization. We are incredible problem solvers, that have to repeat discovery of solutions over and over again because we fail to communicate their solutions or situations.