I think there's a tendency to dismiss this argument in the XMPP community (but there's a lot of truth to it, I choose to use the XMPP desktop clients but none of them are as nice to use as any big commercial IM providers client), but also a tendency for people to make this argument without realizing that they're comparing open source projects run by one or two people to VC funded projects with a company backing them. Of course Discord or Element or whatever will be "better" in some ways, they have a team and millions of VC funding behind them. However, one of the many reasons I chose to use XMPP back in the day when I was first evaluating whether to use it or Matrix, and one of the big reasons I got more heavily involved in the community later, was specifically because the standards body wasn't strictly tied to a company looking for VC funding (and all the individual client/server projects I've contributed to are the same). But, this does mean there aren't really any clients that I'm in love with (but there are clients for every random niche platform imaginable, which I think is probably more important personally).
All that being said, try Snikket if you haven't. It's relatively new, but I think they're really doing a good job of creating a suite of clients that can be recommended to "normies" who don't want to sacrifice shiny graphics for the sake of using something that's a bit more free from VC influence.
There are a number of companies in the ecosystem. Most have chosen not to pursue VC money in order to keep things going much longer. While a venture backed company can have success, most flame out eventually in my observation.
On Debian and derived systems, you can just 'apt install prosody-modules', and on other systems you can 'prosodyctl install mod_cloud_notify' or otherwise download it directly: https://modules.prosody.im/mod_cloud_notify (no configuration is necessary apart from adding it to the module list in your config).
I really like Prosody because it was trivial to reuse the same user store I use for Postfix/Dovecot so every email account gets an XMPP account automatically.
> I am really surprised there isn't a venture backed company pushing XMPP forward. Maybe people have tried and realized it's not viable.
Actually, WhatsApp would fulfill your definition there. They are/were a startup whose entire product/platform is an xmpp client (using their centralized server/instance). Now, whether they pushed "xmpp forward", or merely would be considered pushing a chat platform and who cares whats under the covers...well, that i leave as an exercise for you or others to decide/opine. ;-)
JMP/Snikket for tying a normal phone number to your XMPP @ are really convenient, but the clients remain a problem. Plus, SIP dialers are not supported on IOS afaik.
I am really surprised there isn't a venture backed company pushing XMPP forward. Maybe people have tried and realized it's not viable.