As @sidjohn1 mentions, one of the huge advantages of mesh is that many different devices can act as repeaters while also performing their primary function. Light switches, power receptacles, many relays, even some light bulbs. It’s rare to buy a device that is only a repeater, although may deploy a signal amplifier. But even that is pretty rare since you don’t need to talk to the hub, just the next hop. (Again, not a star or tree topology. Short low power hops work fine.) pretty much any mains powered device will act as a repeater with the exception of smoke alarms and similar devices, where the manufacturer wants to be sure a primary alert isn’t missed because the device is busy repeating a lower priority message.
Both zwave plus and zigbee 3 (next generations) are promising longer range at lower power draw. 4 hops should be enough to cover most houses.
See: