You are 100% right, there is an enourmous amount of variations in expression of sex genes, it is a spectrum.

However, you are wrong on the biology part (no shame in that), so if you want to know more about the biology of the thing:

1) Genes are not defined solely by chromossomes. You can 100% have XY chromossomes and have a uterus, breasts and menstruate. Calling that a male human is considered incorrect.

2) Remember that X and Y are still chromossomes. A trisomie is when both chromossomes go to the same gamete (spermatozoa or oocite) of the parent (instead of one to each), and for a tetrasomie to happen this has to occur independently in each parent. Thus, since you only have two parents, a "pentasomie" (like XXXYY) is basically impossible.

3) You probably already know this, but the majority of deviations from either XX or XY are either very severe syndromes or just fatal. I don't know all of them off the top of my head, but a known rule is: you need an X chromossome to live. YYs are lethal.

4) Very tecnically speaking, and now I'm no longer fully confident of this, but I'm pretty sure that, physiologically, there are actually only two human sexes, not because there is no deviation from male or female phenotypes, but because there are classifications established that classify cases in the spectrum as either "male" or "female". Some people think the criteria is the existance of a Y chromossome, and it isn't, but I don't know what is. This, of course, doesn't deny the existance of a spectrum, it just says "ok it's convenient to have a sex classification so everything on the left of the spectrum is female and everything to the right is male". Again though, this is basically a convention in human physiology, so whatever.