I think you misunderstand something here.

Both conservatives and liberals have a neoliberal economic system that was introduced by Reagan iand Thatcher. That economic system has destroyed both American and the UK.

Progressivism is the same mixed economic system that both the US and the UK had before the advent of Thatcher and Reagan. It was what made the middle classes so very prosperous and what decreased the level of prosperity.

What differentiates progressives from liberals is the economic system - the progressives want to revert to the economic system that existed in America between about 1890 and 1975 and the liberals want to stick to the economic system that Reagan introduced.

The problem is that most liberals have no idea about this, and they've been brainwashed to belive that progressivism is extreme.

I'd be really interested in what you think is extreme.