On the other hand, this technology has been around for 30 years. The feature in question reaches back to the earliest mobile phones. Not smartphones - think earlier than Nokia 3310.
On the gripping hand, "silence.mp3" has been the solution for the author's "mom problem" for a good 20 years too. I hope they don't mean to imply you can't assign individual ringtones to contacts on stock Android? Even the K800i I had as a teenager supported that.
On the yet another hand (we're moving fast into octopod territory here), for a moment here I was wondering what the author was smoking with the "ringtone & notifications" complaint. I don't remember seeing an Android phone that did not have separate volume slider for each. Then I realized, I never actually owned a stock Android phone. Still, to support the author's point against Google specifically, Samsung managed to not have this problem for at least 10 years now.