First, I think the notion that Slavs who died are forgotten about it a bit off. Any high school textbook (at least the ones I've seen) may talk about Jewish victims first, but other victims are definitely included in the conversation.

Anyway, just comparing numbers in this context is incredibly misleading. Most of those Russians killed were either killed in the war or were POWs (so they were killed in battle, or were starved after capture, but were combatants at some point). I'm really not sure where you got your number of Poles killed--that seems significantly inflated. Numbers I've seen for non-Jewish Nazi victims are usually 5-6 million overall, excluding Soviet troops. Perhaps your numbers include Jews from Poland under Polish deaths, and Soviet ones under Soviet deaths? Wikipedia even includes the Soviet occupied parts of Poland under Soviet deaths, if that's what you're referring to.

But the big reason those numbers are misleading is because there were far fewer Jews in Europe than those other groups. Yes, many Poles were rounded up and shot, many Russians were starved, etc. But virtually the entire Jewish population was subject to those things in a way other populations (except perhaps the Roma) were not. While Eastern Europe was devastated, there were still Poles in Poland, still Russians in Russia, still Ukrainians in Ukraine, etc. But huge swaths of the Jewish population were entirely wiped out, such that the areas with the largest Jewish community have virtually none today. That's a level of devastation simply not experienced on a large scale among Eastern European non-Jews.