Loquats. Not sure it's simplicity that's the issue here, though they are--nearly care-free in our area, pest-resistant, drought-tolerant, only a small rust issue that can often be outwaited. They're sold as ornamentals with no mention of the edible fruits on nursery cards, and a lot of the folks who grow them don't know that they can be eaten, or don't care.
Or, perhaps, believe me. One guy told me "If it was food, it'd be at the grocery store." I thought about buying him the canned (product of Mexico, bottled in syrup) loquats our local chain grocery carries in its very own store brand, but...
DSF
Austin, TX