I caveated my comments as opinion.
Been there, done that.
I have no need for residential WiFi... my router + one AP provide all that's needed.
More than you want to know, below.
Capacity is limited by the available (idle) air time on/near the channel the access device is using (of course). Single-radio mesh nodes are terrible at this, as the backhaul and access is done on the same radio. Two-band mesh nodes, often 5GHz for backhaul, are much better. But dual radio mesh nodes are an overkill for residential users, esp. when prudence has big bandwidth consuming desktops and immobile devices using wired, and low demand handhelds, on WiFi. Or a casual use laptop. Even streaming Netflix is low demand.
I spent a long year working as the principle engineer for two big cities, as a consultant to Earthlink. That was a mashup of Tropos outdoor meshing (good), and Motorola's Canopy (er, ah, not so good) for backhaul. As we know, these metro WiFi projects all died for lack of a viable business model. Technology wise, this was very interesting and challenging, esp. for cities with serious terrain/mesas. It was all about building penetration and how to get whole house coverage at reasonable speed - at a CPE price that was not sky-high. Self-install was essential to the business model and it just couldn't be done.
I also worked for years on military mesh networking - where every node moved, most as pedestrians. That got so much money, and cost was tolerable and stratospheric levels, that it sort of worked. But the need came from mobile nodes, no fixed infrastructure -- not the case with consumer WiFi.