I think it's just a pretty consolidated space? Kind of like ebook management, which was dominated by Calibre for so many years (this changed recently).
But unlike ebooks, media centre management is a fair bit more complex since it involves supporting many different media formats and many forms of acceleration or transcoding.
So the big projects - Kodi for local media and Jellyfin for streaming - have a lot of inertia because they tend to support whatever you throw at them.
It’s not that difficult to be honest. VLC / ffmpeg can do most of the heavy lifting. And there’s no shortage of libraries for rendering in a UI.
There used to be dozens of options to choose from. Multiple different XBMC forks. Multiples different Subsonic forks. Multiple different DNLA servers. Multitudes of web-based servers. CLI MP3 servers. Independent media centres for a variety of different consoles.
Maybe that’s still available and just not indexed on that site. But I noticed the choices had shrank significantly last year when I was looking for Plex alternatives compared with when I last built a media centre approximately 15 years ago.
Maybe smart TVs have reduced people’s desire here?
It's logical, but the low variety is disappointing nonetheless and makes it more likely than none of the available options are well-suited to one's needs/desires.
In the case of media management, ffmpeg is easily usable with just about every programming language in existence and its usage is extremely well-trodden at this point, which makes the vacuum of newer alternatives to the XBMC lineage all the more puzzling.
What did the ebook space change into?