>like the package manager
It wasn't about, for example, dpkg vs rpm, but apt-get versus.. nothing, because Red Hat had nothing to solve dependencies. Installing software on Red Hat was a truly hellish experience.
>default filesysem
I have never in my life seen people dismiss a distro because of a default filesystem. I question whether you've truly experienced the early days of Red Hat.
They shipped broken development snapshots of GCC that led to serious compatibility issues :
https://linux.slashdot.org/story/00/10/07/0027218/gccs-respo...
They employed one of the most abrasive and divisive personality to helm the development of the libc :
https://news.ycombinator.com/item?id=2380062
They were one of the most barebones distro in terms of tooling to configure and manage them. Debian was more fully featured on the terminal tooling front, while Mandrake and SUSE had a lot of GUI wizards for people more used to the Windows ways.
Even much later in the Fedora days, when Kernel developer Alanx Cox questions the sanity of releasing a completely broken distro (version 18 of Fedora) this is what they had to answer :
>So yeah: in case you didn't get the memo, F18 has a new installer and a new upgrade tool. They are both v1.0s. As in the case of all v1.0s, you may want to exercise some frickin' caution. If you want a Fedora release whose installer and upgrade tools were stabilized over a period of several years and 20+ releases, Fedora 17 is right in the torrent list
Uh, like.. okay? but maybe don't release it, until, you know, it's not garbage?
And then there's the whole thing with what Red Had did to take over the whole userland desktop stack with systemd, logind, dbus, pulseaudio, wayland.. all of which caused more issues than they ever solved. You still can't make software like autohotkey on wayland. All those pieces of software are heavily interconnected with each other making it less and less tenable to maintain a distro that doesn't package them.
There are many, many reasons to be soured with what Red Hat contributed to linux.