Extremely not-fun fact: collectively, humanity currently produces more than enough food for every person. But a huge part of it is either wasted or inaccessible by people that need them, which usually results in them not going to anyone and being wasted, which is why we still have food scarcity.
Fruit trees been around longer than we have, they can care for themselves
Not the cultivated fruit trees that have been selectively bred by humans for thousands of years, no.
Yeah, they grow just fine. I dont know what you think they cant get without human care
Most crops are very different from the wild plants they evolved from. In general, the domesticated varieties are softer - they need fertilisers and pesticides, sometimes even manual pollination. Without this they would be outcompeted by wild plants.
Its not as general as that, no. Theyre often bred to be more naturally pest and disease resistant. If youve ever tried growing heirloom tomatoes vs hybrids. They dont have higher soil nutrient needs either.
There are exceptions, but a general rule is that if you invest more resources in growth your investment in pest defence will go down. So plants bred for yield often have reduced pest tolerance. But yes, they are in many cases interbred with more resistant varieties to (partially) compensate.