I suppose it might seem like that if you install it just for a singular app. Then the runtime + possible drivers are a hefty load. But everything after that, the weight of the deps proportional to the apps gets lighter through shared runtimes, drivers, dedupping and so on.

Some go to install a singular flatpak and are horrified by the amount it tries to install and never look back. Which I sorta get, though if that their level of familiarity with flatpak they might not be the best people to partake in the dep/flatpak/snap/appimage fights. But they still do.