Humanism is a good philosophy for the modern world. It can replace religion because it is more modern and answers questions which religion sometimes can't answer. People do not have to follow antiquated religions to be spiritual these days. Humanism is a good philosophy that is not weighed down by anachronistic rules.
Humanism can be an alternative to religion for those that chose to follow that path. Humanism inlcudes some of the same facets of religion, as far as making the right decisions and being good to other people. It may not be suitable for all people, but humanism can be a good basis for those that chose to avoid religion.