Chicken and the egg. If you're sufficiently close to people to convince them to use SMS/Signal/Matrix/whatever with you, then sure, you'll be fine. But what if you're not? What if it's either "install WhatsApp and join our group chat" or nothing?
I don't. Everybody got a phone number, sms and email. So if we don't share a tool, I fall back to that, to face to face, accept a delay or be left out of the loop.
The secret is to focus on quality, not quantity, and realize a lot of FOMO is involved.
If the quantity is zero, the quality doesn't matter - if the alternative to joining the group is to be left out of the loop, there is practically no choice.
For example, if they write - in the group - that the next meeting is 3 PM next Wednesday at so-and-so, unless you happen to run into them at that specific time your chances of knowing this are slim.
