Where's the problem here? Too many options and too much control? Nothing's stopping you from blasting every group chat you're in other than that you'll annoy the people in chats that don't want to hear about your problems. Maybe just send to your family and close friends.
> now some people get the same update twice - are they supposed to react in both?
This is a non-problem. Do people have to react to everything you say every place where you've said it? Is it difficult to decide how to deal with getting news over the phone and having that person announce the same news at the book club meeting? How will you know where to answer?
You could say “if you don’t think people care, only tell your close family and friends”. But broadcast announcements can cause more spontaneous reactions from people, and I often find myself reconnecting, even if only in a short conversation, with people I don’t generally talk to otherwise. It’s a better way for staying connected with old friends, who you might not have reason to talk to frequently (e.g. via group chat), but would happily spend a day catching up with if you were in the same city.
My intimate friends are almost all in group chats. Many of them are not technical at all.
People would announce things like that to each group individually, and often chose to not mention it in some groups because they're not intimate enough. We used to just be okay hearing and discussing the same announcement multiple times ("some of you already know this, but..."), most likely with different parts of the story told in different settings and triggering different conversation because the groups are different.
For the more distant acquaintances, people wrote Christmas cards (or equivalent) for the occasional updates. These can still be handled very nicely with an email list, and really don't call for the kind of instant-update sharing that Facebook et al encourage.
Is it less efficient to write and read the same updates multiple times? Sure. But is efficiency really what we should be striving for in human relations?
The value that Facebook brought is now people can _choose_ to respond to you, and you can also silently see what others are up to without needing to explicitly catch up. It’s kind of like bumping into someone you know in public, and the resulting interaction (e.g. comment or DM from seeing the update post) feels much more organic as well.
WhatsApp, at least, makes it easy to post the same update to multiple groups.
Group chats are intimate by design and don’t seem like a good fit for “broadcast” style updates like “I bought a house”, “moved to CA”, etc. That’s the value in the Facebook feed of old. Something like that also helps you stay connected with more distant friends/acquaintances, people you might not talk to daily but you would still be happy to see how they are doing in life.