Haters aren't worth listening to. Doesn't matter if it is flatpak, systemd, wayland, or whatever else. These people have no interest in a discussion about merits and drawbacks of a given solution. They just want to be angry about something.
I'm a Debian fan, and even I think it's absolutely preferable that app developers publish a Flatpak over the mildly janky mess of adding a new APT source. (It used to be simple and beautiful, just stick a new file in APT sources. Now Debian insists we add the GPG keys manually. Like cavemen.)
If you're separating your application from the core system package manager and shared libraries, there had better be a good and specific reason for it (e.g. the app needs to be containerized for stability/security/weird dependency). If an app can't be centrally managed I don't want it on my system, with grudging exceptions.
Chocolatey has even made this possible in Windows, and lately for my Windows environments if I can't install an application through chocolatey then I'll try to find an alternative that I can. Package managers are absolutely superior to independent application installs.
I'm new to Linux. Every time I've had a major issue with an application it turned out to be due to a flatpak. I'll stick with other options for the time being.
Are those flatpak haters that say that in the room with us right now? The main difference with distro repos is that packages in it are packaged by the distro packagers and everyone who has an opinion on flatpak should know that this is how it works.
You don't need the distro to package your sodtware through their package management systems though. Apt and dnf repositories are extensible, anyone can publish. If you go to copr or ppa you can have a little extra help too, without distro maintainers.
The headache comes up when multiple third party repositories start conflicting with each other when you add enough of them, despite they're best efforts. This scenario starts needing flatpack, which can, for example concurrently provide multiple distinct library versions installed that traditionally would conflict with each other. This doesn't mean application has to bundle the dependency, that dependency can still be external to the package and independently updated, it just means conflicts can be gracefully handled.
I know nothing about how flatpak works other than that it's containerized. But this meme tells me it's the OS's responsibility to create the flatpak, and not the developer's? Is that right?