Philospher-
In Biblical times, people gave far more than 10%. Your forgetting Leket, Shikcha, Peah, Bikkurim, Terumah, Maaser Rishon, Maaser Sheini/Oni, Challa, Maaser Behiemos, Zeroah, Lechyayim Vekeyva…. The list goes on….
Do you find that disgusting and immoral too?