One of the qualities of large institutions like churches is that they are incapable of making sudden changes in their policies even if they know that their current policy is wrong. Instead what they do is slowly edge towards a new policy by incremental steps, each time claiming that it is as far as they can go or is theologically justified.
This is particularly true of quasi-democratic religious institutions that have voting rules for decision-making. Take for example the Church of England, the parent organization of the worldwide Anglican communion. It is pretty obvious that it is going to end up with full equality for women and gays. But it cannot quite come to terms with it just yet, so it backs and fills towards it, like someone slowly immersing more and more of their body into cold water rather than plunging straight in.
We saw how a few months ago, the General Synod narrowly defeated a proposed change to allow women bishops even though women clergy have long been a part of the church. Is there any doubt that this change will come about in the near future, definitely by the next Synod if not sooner?
Similarly, the church had accepted gay clergy and allowed them to become bishops but had prohibited them from entering into the civil unions that are allowed by law in the UK. But in December the church decided to drop that ban too but again they held back a bit, saying that bishops in such unions had to remain celibate, a truly bizarre contortion. (On the positive side, the National Cathedral in Washington DC has announced that it will allow same-sex marriage ceremonies to be conducted, which is quite a significant step, given the symbolism of the cathedral.)
Oddly enough, the more authoritarian religious institutions like the Mormons and the Catholics that take direction from a single individual can in principle change more easily than those without a hierarchical structure because all it takes is for their leader to have a ‘divine revelation’ announcing a change in their god’s will and most of their followers will fall in line. It is more difficult with evangelical Christians and Muslims and Hindus and Buddhists because they do not have such a centralized decision-making structure.