The death of Neil Armstrong wasn’t ignored. The second he died, and for some time thereafter, this was the lead story on every newsbreak, on every tv screen news crawler, etc. I heard it, I saw it, it was dominant.
What happened is that people have gone on from there in a somewhat understated way, not like Kennedy, King, etc being assassinated. The circumstances of Armstrong’s death at 82, from heart disease, wasn’t shocking. He had lived as long as his body was able, so he passed from this life, and his enormous achievement was noted.
Beyond that, where would you go? Neil Armstrong was very understated and hated personal publicity. The man would not want anything more than what he received. He was PAINFULLy against anything more than that in life, and no doubt, in death.