Ubuntu might be the most popular linux distro, but there's so many other options out there. Take a look at https://distrowatch.com/ there's basically a distribution for any type of usecase you might imagine. Hell if you can't find a distribution to suit your needs nothings stopping you from starting your own.
Using 'dogs' and 'poodles' interchangeably subconsciously implies that all/most dogs are poodles.
I think the big difference here is the relative mindshare of Windows in the Windows ecosystem (100%) vs the share of Ubuntu in the Linux ecosystem (popular and dominiant, but not 100%).
A very small portion of the Linux community made the decision to put the launcher ads in, a large chunk of the community made a very loud fuss, and the feature was removed.
Why not? Ubuntu (along with Red Hat & others) is a commercial distribution of Linux, but it's not the only Linux. Users who care about their freedom & privacy don't use Ubuntu, because it includes proprietary drivers & does things like phone home.
Users of distros such as Debian, OTOH, do care about those things, and I think it's very fair for us to note that we find the behaviour of Microsoft recently to be quite remarkably sad.
If I start selling beer with piss in it, does suddenly all beer taste like piss or just the one I'm selling?
Debian's momentum is due to the fact that it's a really stable, really well-thought-out, sysadmin-friendly, production-quality, freedom-respecting, privacy-respecting Linux distro; I don't think that has changed, and I don't think that anything beats them by those metrics.
Ubuntu's momentum is due to the fact that it supports proprietary hardware, is easy to use, and is pretty. You may be right that other distros are better than it there.
Debian & Ubuntu are very different.