I'm actually not even fully sure on the details what they even do that isn't in Debian aside from maybe some driver stuff and assorted annoyances like Snaps. I just know to stick with Ubuntu derivatives because almost all large popular apps seem to be well tested and designed to work on it, until the community gets tired of it and probably Fedora or something takes over.
It's the perfect example of "I'd rather have a mediocre standard than something excellent but obscure".
I'm not a fan of Pulse, because of its lack of low latency, although It still offers a lot over raw ALSA, and PipeWire solves basically all of it's issues.
But systemd is a lot more comprehensive, it doesn't seem to leave any use cases out, aside from ultralight embedded and old school "Control everything yourself with imperative scripting" style setups.
I just think Poettering's (and, more generally, Red Hat's) taste is really bad, so I wish it weren't him(/them). Possibly when they finally achieve Systemd/Linux and the entire stack atop the kernel is stuff Red Hat likes & directs it'll all be worth it, I dunno.
FWIW I also haven't much cared for a lot of Ubuntu's attempts to steer the direction of Linux—they've just lost so badly at every attempt, that it hardly matters.