I’m not advocating for there to be no more religion - I just wonder if religion was replaced with humanism one person at a time, would the world be actually worse for it. I don’t think so but many others might think differently because of the millennia-old Christian orthodox belief that humans are naturally wretched without the saving grace of a god.
Believing you’re wretched can indoctrinate people to act accordingly. That's why it is sometimes said that if one deconverts from their religious beliefs, they will no longer have morals and, therefore, begin to behave more immorally. This religious bias-based logic is simply false.
When humanism is encouraged instead of such beliefs, the idea of “the potential value and goodness of human beings” would help people to “emphasize common human needs” and promote “solely rational ways of solving human problems.” (Quotes are from the definition of humanism by the Oxford dictionary) In that sense, I think the world would be better off.
One other thing, I often hear the point being made that unbelievers can do the good works that believers of all religions do, but in contrast, they will not do the harmful works that these believers can do to themselves and to others because of their beliefs.