I live in BC, Canada, and here you can find apples, a large variety of berries, pears, plumbs... All growing in random open areas and all delicious and relatively pest free without any pesticides. Even though a lot of those aren't native they seem to do pretty well. Perhaps the fact they're not grown commercially in this area helps... I grew up in Israel where pests were definitely more of a problem but you could still grow many different fruits without using pesticides and I used to pick many fruit off trees for eating... (Mangoes, oranges, and many more). Some of those "large" grocery apples have no taste and a floury texture though we do get some local apples in season here that are good...
Monocultures is a big problem. If you have a good mix you're less likely to have serious issues. It can still happen but less likely. You also need to take care of your trees, prune them, water them etc. if you want to get good fruit... Just let them grow doesn't always work...