If you are selling a house you have to list on rightmove. You're not going to choose to list on fewer sites. The question then comes if you're selling, why list anywhere else.

As a buyer it's terrible - I want to be able to see size of property (from the EPC, as I trust that more than the estate agent), the sale history, the EPC data, the council tax band, the map of the plot.

I can find that all out manually by hunting for the real address and going from there, but it should be there directly (and filterable)

As a seller you're forced to use rightmove as that's where all the buyers are

As a buyer you're forced to use rightmove as that's where all the sellers are

As a competitor how can you argue to an estate agent they should spend money with you as well as rightmove