There should be an option to customize the devices that are available to play. Delete at least those that we don't want.
I currently have multiple devices at home that support Google Cast and Spotify Connect but only use a few of them. It is very annoying to have to search for the device I want in a list full of devices that I will not use. Obviously I want those devices to remain connected to my network.
It is also annoying that devices such as my PlayStation 4 appear in this list. I have logged out. Unlinked my Spotify and PlayStation accounts. I have completely formatted my PlayStation. I have cleared the cache and reinstalled Spotify on mobile. Still, it continues to appear as a device available in gray even if I can't use it.