That's because it was the only game in town -- its not like there was a choice of denominations, or anything.
Now, if the Presbyterians go apostate, the Baptists are down the road. If the Methodists go apostate, there's a servicable Wesleyan church not far away.
It's a different world now than then.
One shouldn't just give up because of tares in the wheat. That certainly isn't the stance of Jesus' parable on the same subject.
Is there a time when I WOULD leave....absolutely. And I'd call it the Reformed Methodist or something like that.
BUT...someone give us a legal strategy for a quick seizure of leadership OR understand that the current polity will make any change slow OR encourage everyone immediately to leave their churches whenever the church makes bad decisions.