Dark pools mean that public market prices aren't as accurate. The story of financial markets being valuable to wider society is, among other things, price discovery. Dark pools don't serve that purpose.

Moreover, the PFOF story depends on 'price improvement'. If public stock markets aren't accurate, then 'price improvement' is a meaningless concept, because it compares the price to the public stock market price.

> It’s no different than telling your neighbor you’re willing to sell your house for $X without publicly listing it.

The difference is that the most accurate price for 'my house' is not of significant public value. Whilst the most accurate price for stocks is quite valuable to the wider world.