The requirement for citizenship as a spouse of a UKC is being resident in the UK for 3 years and having ILR.
Under the old rules, when you could apply for ILR after 2 years on a spouse visa, the time to citizenship was typically 3 years for most people: 2 years on the spouse visa + 1 year ILR. If you were already in the UK on a fiance(e) visa, student, visitor, etc - you could apply for citizenship sooner.
Under the new rules, since it now takes 5 years to qualify for ILR, you have to wait until you have ILR to apply for citizenship, but once you have ILR, you could apply for citizenship immediately since you've already accumulated the necessary 3 years UK residence.