Discrimination in hiring happens every day. Be it conscious or subconscious. If there isn't a hard, unavoidable quota no one can force anyone to hire people they don't like. The laws may just forbid them from being this forthright.
Never attribute to malice what you can more appropriately attribute to stupidity. The people who coded this may be young and not even on their first divorce yet. To me, that's what this family plan business falls under. To leap from that to organized discrimination of folks being born out of wedlock seems a tad too conspiratorial from my POV.
This may be a fryable fish. Yet I see much bigger fish elsewhere.
What may also hold back development of functional patchwork family plans is legal hot water. Not every split is amicable. The Googles and Microsofts may simply have decided they don't want to be put in a situation where they need to adjudicate between two warring ex partners whose bitterness is overriding their child rearing responsibilities with petty disputes. And building a system where maybe new partners can gain access - even just by mistake - to their spouse's kids accounts also has very bad PR potential when it turns out the step parent is abusive.
Nevertheless you should let them know about your feedback. Patchwork families are quite common and they can probably do more in that area.
First of all, this isn't enshitification as defined by Corey Doctorow. This has nothing to do with an internet platform getting worse because the priorities of the proprietors changed.
I don't think it's entirely fair to blame Google for this. None of these companies do this for entirely altruistic reasons. At the core of the problem is funding in education. Google saw an opportunity and jumped on it. When given a choice that kids get no computer hardware vs. dumping price Chromebooks I would still vote Chromebook. Get your politicians to set aside less money for tanks and more money for education.
Besides, no one is stopping kids from exploring other platforms. Google is looking for an infrastructure lock-in, get them locked in while they are young, but you can go do other stuff. It's also a question of financial means and interests. And they don't need to do LAN parties because they already have Fortnite and stuff. Life moves on. Your childhood was also markedly different from your parents'.