(This is a half-rant half actual question)
I wanted a nice qt theme to use on Scribus since Arc Dark doesn’t work on there. When I tried to install it, pacman said this will install 50 packages. 300 Mb in total.
Why does a theme need packages such as Kauth and Kwallet?
If you use Flatpak from the start, the storage thing becomes less of an issue.
Flatpak only takes considerably more space because people use Flatpak as a last resort or too late into the life of the current installation, as flatpak will have too many requirements for too little apps.
It is accurate that the first few flatpaks will use proportionally more storage as you will need more basic resources but you will will always be using substantially more storage than traditional apps. That said storage is cheap and the correct answer is to buy more instead of choosing tech based on storage requirements.