Signal declined, despite the EU bending over backwards and handing them the chance on a silver platter to become relevant.
IMO it's a mistake, like getting rid of SMS support was (which is far less secure than WhatsApp yet Reddit/Lemmy seem to be angry about that but glad about lack of WhatsApp interoperability?? I guess it's because Americans don't really use WhatsApp so it's not a big deal to them, whereas SMS is).
It would have been an amazing opportunity to help those that want to use Signal actually use it.
Yes, I'm aware Meta scrapes what metadata they can from messages, but if you make this clear in Signal when you talk to a WhatsApp user then I don't see the issue, after all it's what they did for SMS chats yet everybody loved that feature!
People trying Signal because it's compatible with WhatsApp that everybody uses would lead to more Signal-to-Signal chats, and that's a good thing.
The Signal foundation seems to care more about being ideologically pure for its 10 users than they do about making a small compromise that leads to far more users and far more Signal-to-Signal chats. It seriously disappointed me, and I stopped my £10 monthly donation hearing that bad news. I was so invested in Signal because I thought it was a great app, but there's no point of financially supporting the growth of an organisation that vehemently rejects growth, I was throwing my money away.
I went from having 10 contacts on Signal down to just one after the SMS purge. I want to use this app but it's pointless. Nobody wants to use an app that nobody uses, and Signal doesn't seem to want any users either.
Frankly, I don't buy their excuse. If they were truly that ideologically pure about absolute privacy, they'd never have added SMS support in the first place! And they wouldn't have tied accounts to phone numbers either!
I think the reason they ditched SMS was down to development costs. Maintaining that functionality, as well as building RCS support, is far more expensive than simply cutting the feature out and trying to salvage some "it's about privacy!" PR. I think the same is true for WhatsApp integration.
E: I knew this would start getting heavily downvoted once the Americans started logging on. Please try to understand that WhatsApp is big in much of the world. Everybody uses it. My bank wouldn't let me take out a mortgage without WhatsApp. That's how ingrained it is. Being able to use Signal and still receive messages from people would go a long way in getting people to install the app.