I see problem in that only in unmaintained apps (like org.gnome.Dictionary), I have only GNOME 47 & 48 for example and both of them still updating

More precisely, it almost never does.

I don’t know any flatpak in my system that don’t use runtime (I have around 50 flatpak apps installed), or am I misunderstanding your point

Flatpak is not single binary, Flatpaks have shared runtime (For example Freedesktop, GNOME, KDE runtimes)

What the point of using Gentoo with Binary packages?

Also Lotus is very cool!

Fedora have “Enable 3rd party repositories” button in post-installation user setup which enables NVIDIA, Steam, Google Chrome and Flathub repositories. Then all of these can be installed from KDE Discover or GNOME Software, no need for terminal