Apple is recommending mesh routers for larger homes. I have a large home and I currently have 3 x AirPort Extreme base stations (802.11ac) in my home that are connected to one another via wired gigabit ethernet backbone.
Is there anything I am missing out on that these mesh routers can do? It seems they are only handy for people who don't have their homes wired for gigabit ethernet. Any other advantages?
Nope in fact your setup is better than mesh IMHO. Your setup will be faster ultimately thanks to the wired backbone. Best approach is still wired backbone with multiple access points. Mesh is really for situations you cant setup a wired backbone.