Well, well, well.
I wasn't around in the early 00s, but from what I can tell, the "FLOSS-game-scene" clearly has shrunken quite a bit. Many of the points farrer made ring true to me - additional factors might be the increased complexity and expectations towards video games, the wearing out of the technical edge that the release of the Quake3-Sourcecode brought to the community, and the breaking away of the Linux community from FLOSS gaming.
But: If you only look at the source code/binary side of things, I'd say that there are more games with a FLOSS base than ever before; not just Godot, but also Twine, Bitsy, and various smaller game engines. Most of the people who use them do not identify with the FLOSS scene, though, but if we only take the fundamental definition of free software/games, I'd argue that there are much more now than in 2005.
If you ignore these, and only count games that were intentionally made as "Open Source" games, you can also find some within the whole indie space, and I've seen a few where the devs were convinced FLOSS-advocates - but most of them aren't connected to the scene here (this forum, the blog, the LibreGameWiki). "Fully Libre" games are, however, scarce (many small productions use assets that were either bought, are used with unclear licensing, or were made for the game - in the first two cases, they can hardly be rereleased under a new license, in the last case there is no clear benefit from turning them free for the devs, and thus it is seldom done).
All of these newer "free games" are usually smaller and less elaborated than the "old flagships", but are usually more unique when it comes to design and gameplay (which I consider overall a good thing).
I believe that one of the problems of FLOSS gaming is that most of the people who associate with it are mainly developers; there ain't much discussion about the games released, and multiplayer servers tend to be empty - which is a vicious cycle, as it reduces the attractivity for both new devs and players to interact with the scene. I think that things like the "OnFoss"-events are a good idea, although I didn't manage to partake at one until now :3.