Your post has really got me thinking and I went on a bit of a numbers hunt. Sorry, not sorry, for the huge nerdiness to follow.
tl;dr version - There are a lot more games to spread players over, but probably more players too.
___
The long version:
According to the BGA round-up email, they released 142 games in 2024. I'd guess it was roughly the same the year before. That means the games library has grown by a third since you were previously around. This is already a much bigger pool of games to spread people over.
In the absence of other official numbers *, I thought I would use Arena players as a proxy for activity / player numbers.
Catan, unarguably one of the most popular board games of the modern era, was released on BGA in the second quarter of 2022. Its first season saw 5,732 players and has grown steadily to the point that for the past year, it's had four seasons of over 10,000 players each.
Azul shows a similar pattern, but even moreso - from 8,000ish to a steady year's worth of 16,000+ players.
My most-played game, Copenhagen, got its full release to the site one season before Catan. It got a peak of 838 players in the following Arena season, but has seen steady drop-off since. Last season, there were 210.
Akropolis, released in the first half of 2023, also showed declining numbers in the Arena - 1,136 to 778 in season 18. However, season 19 saw a boost to 958, presumably because the release of the Athena expansion gave it a fresh hit of publicity.
I'd theorise that the overall number of players are increasing, as shown by the most popular games' increased player counts, but the more niche titles have to fight for attention against a steady stream of novelty, sometimes accompanied by some serious industry buzz (I'm looking at you, Harmonies).
My personal experience (having joined around the time you took your leave) is that the chat has always been pretty quiet, but I specifically sought out communities that foster friendliness and as a result, have made some lovely connections. My own playing style has switched to majority turn-based now, and I can think of only one situation that I couldn't get a table for a game I was interested in (and I've tried over 300).
___
* Although if anyone knows of easily accessible historical figures, I'd love to see them!