Humans were foolish.
Humans were foolish to the point where there was no saving them. As long as there were humans, humans would be foolish. This was something innate to humans, a sin that wouldn't disappear until death.
Only cleansing and evolution would be able to eliminate the sin of foolishness within human souls.
The only path forward was to cleanse the old humans and evolve into new humans, becoming a completely new species!
Shinzen Tendo had long since believed this.
Yet, he knew that he was also a foolish human. He could only sigh about his own lack of intelligence and strength.
It was probably his limit to only be able to minorly cleanse or evolve himself despite all the hard work he put in.
Shinzen had this self-realization as he silently worked hard and lived a life that wouldn't attract any attention.