To begin with, I think some soils could support even vegetable crops without having to add anything. My soil could not. I have worked very hard making compost now for several years, and still in my vegetable patch I have to add chemical fertilizer to really be productive. My flower beds could probably get by without any chemical fertilizer, but I still get better results when I use them.
So I think some people can just use compost and compost tea and do very well, others will not be able to be very productive doing that.
I think compost is wonderful stuff, I use a whole lot of it and I love the results I see in the change in soil texture, but in my garden I use it mostly for a soil conditioner not so much for nutritional value.
I have had a hard time learning not to over do when using chemical fertilizers, but I you can remember to just use teaspoons and tablespoons instead of double handfuls you will normally be alright.
I think that is the main lesson to be learned, use chemical fertilizers in moderation and don't go by the theory that if a little is good more is better, because that just is not true.
