>can they clean hard to reach spots behind doors

Robovacs aren't a drop-in replacement for a maid, they aren't a fire and forget cleaning solution for a house that's already dirty and messy or have constant spills and stuff left on the floor, but more for regular maintenance of an orderly place that still gets cleaned or maintained in the tough to reach places every now and then.

But if your place resembles a crack house, a robovac won't magically clean it.