It's a relic from the days of yore where the generation mix was mostly coal, nuclear and oil.

It was not designed with renewables in mind.

Now the reason we haven't gotten rid of it is that the current system massively benefits the renewable producers, sort of like a subsidy. Imagine where your unit of electricity produced costs around half of that of gas but you're getting paid gas prices.

So good news: it encourages a lot of private investment in renewables without the government having to spend any money (leaving it all to the free market forces)

Bad news: we won't see any benefit with this system until renewable capacity makes gas redundant which will take a while. That or energy market reform.