I saw nothing on the link you posted about iron deficiency. It warns about other things like kidney stones, but there are more than one point of view on this.
I’ve been eating most of the foods advised against on that site and have never had an iron deficiency in my 72 years.
I did have a kidney stone in 2002, but it was likely caused by dehydration. I’ve been eating foods high in oxalates since then without any more stones appearing.
The site you cite reminds me just a bit of the propaganda from the meat industry that tries to discourage people from eating plant foods.
From what I’ve read, only a small percentage of people have problems with oxalates. But I’m always willing to learn more.
Check out: www.naturalnews.com/033078_anemia_iron.html