Over the many years whenever someone discusses Flatpak it was very common to have a link to [1] which lists issues with Flatpak. In the last few years the platform seems to have been improved and is now being used on a lot more systems out-of-the-box like the Steam Deck (with SteamOS) and Fedora also enabling it by default now.

So, do the claims on flatkill.org hold merit still?

[1]: http://flatkill.org/