According to Google, approximately nobody used the federation capabilities of Google Talk except inbound spammers. It was absolutely not "for the masses". The masses all stay entirely within the censored and pruned walled gardens, then and now.
It was all maintenance and antispam burden for no product benefit to users.
Hackers vastly overestimate the desire of users to use federated systems.
This is how I feel when I get an SMS from an email address. There are 0 legitimate people who would message me that way.
I have an entire rant on XMPP in some other HN thread, but basically I agree, chat federation is for nerds. And if XMPP wanted its federation dream to come true, the core standard (not including extensions) needed to be more rigid and keep up with the times. Instead, every sever ended up supporting a very different feature set, usually lacking things you'd take for granted in other chat apps.
Approximately nobody used the federation capabilities because approximately nobody used Google Talk... LOL
In more seriousness, I know of quite a lot of people who chose to use Google Talk specifically because they could use it with their client of choice. (It also had a very wide reach for a while, thanks to its Gmail integration edit: and federation)
I honestly don't know anyone else who used Google Talk (other than whenever they checked their Gmail they'd also see any messages in it).
In other words, Google killed off the two reasons why people used it (edit: reach and choice of client). Since then they've "replaced" pieces of it with multiple different apps (Hangouts, Chat, Allo, Duo, Meet), some of which they're finally deciding to merge back together, and in the process all they've ever done (and all anyone expects them to do with this merger) is remove features. Usually exactly those features which were the only differentiation those services had from the competitors. Which means there's no difference from a competitor with a wider reach (Zoom, 100 different IM apps, iMessage/FaceTime, etc.). Which means it's doomed to be terminated (and probably reincarnated) by Google again in a few years.
(Maybe there was even a third reason to use Talk: it was the IM with Google accounts. I don't think there's been One IM To Rule Them All from Google at any point since then.)
The two reasons were supposed to be reach and client choice. I got a bit side-tracked thinking about whether I should clarify that I was able to reach most of my contacts on it because of the "Gmail integration and federation".
It was all maintenance and antispam burden for no product benefit to users.
Hackers vastly overestimate the desire of users to use federated systems.