I never understood how shared ownership was supposed to work.
If first time buyers can afford, say, £50k, that's what a 2-up-2-down will go for. Create a scheme that means they can afford a £100k house, and the same houses will go up in price to £100k. So the first time buyers spend the same, but only own half the house.
Every scheme based on increasing the spending power of buyers has the same basic flaw of pushing up house prices.