An Aternal Quest?
I've pretty much lost hope we'd ever have a truly global messaging standard. For a while XMPP was aiming for it, but it lost itself in a pick'n'mix assortment of options/add-ons/extensions. That doesn't mean it hasn't been successful behind the scenes, Initial Facebook chat, Whatsapp, Google Chat/hangouts (whatever the flavour at the time) used it, and even interoperated with third party clients. For a while at least. The GSMA has been gagging for a "social"/"messaging" platform for ages to make operators feel non-dumb-pipe. Remember Wired Village (from the days of WAP)?
I pinned my hopes on Signal Protocol being the newer, better XMPP and, again, while it's been successful in underpinning Signal Messenger, Facebook Messenger and WhatsApp, it still hasn't broken the vertical silos/walled gardens of commercial interest. Google's "generous" offer of RCS at least brought some federation across operators, but totally missed the boat on being properly secured and end-to-end encrypted. Something to which operators and governments are still rabidly allergic.
Messaging platforms definitely seem to have a generational clique brand aspect to them, i.e. there are the hot, hip and happening ones and the ones your parents or work/college/institution use. None of those make it easy to have work/life/social splits with the same interface. And people rush where the latest emojis, stickers and such are, cf. the swing onto Telegram and TikTok. I'm sure there's little reason the latter cannot use stock, standard back end protocols, besides the walled garden. In the new cloudy world, perhaps what we need is messaging-as-a-service so anyone can spin up their own, add their own special sauce interface bits to the client, but at least have common, at least technically interoperable back ends. We have the protocols.