Did he really sing 'prophesise'? Surely it's 'prophesy'?

I always felt the song was defiant and dismissive, a sort of thumbing the nose at the establishment, without suggesting anything constructive. A bit 'teenagery' in fact.

I'm sure we have indeed come a long way since those days. Women's liberation and feminism, acceptance and decriminalisation of homosexuality, contraception, reduction of racism for example.
As Steve says, there are other things to address, but there always will be.