Certainly it is more difficult to have a nutritious diet, but not impossible.

The iron thing is true, this is one huge benefit of bfing - there is not a lot of iron in bm, but 98% or so of what is there is absorbed by the body. So we can give our kids a great start by bfing until at least age 2 as recommended by the WHO (I know this isn't possible for all, both my DSs self weaned before age 2, but it's a noble aim). Also, as Dach said, vitamin C helps the absorption of iron. As someone with a condition which means I have high iron, I have seen how dramatically my iron levels can rise if I take multi-vitamins (even those without iron in them!).

Also sourcing your fruit and vegies to get the freshest ones is a good thing. I think growing our own is a good thing to aim for, although again, not possible for everyone. Also think of the environmental impact of being partly self-sufficent - less transport to deliver food etc. Sure, for one person, not much difference, but for a whole community it can have an impact.

Another issue which I am passionate about, is the ability to feed our kids (and our selves) without foods that are high in salt and/or sugar and/or potentially harmful additives. This is next to impossible, especially when they attend parties etc. But again, with some effort, you can do a reasonable job at avoiding these things most of the time.