This is not the problem of the donation system (which I personally miss a lot, sometimes it's fun to share weapons with other people), this is the problem of ks1. These weapons are still quite useless, the flamethrower's fire rate is so low that it can be directly countered with mars2 for example; g5 has 4 ammo, etc. They are basically normal weapons with their own weaknesses.leading to donation being the dominant option for KS1 across even the players who were intended to benefit from it.
Currently when I get ks1 I usually claim g28 which doesn't really help me but at least it doesn't hurt as well, because when I play with something I'm already used to, switching to g5 or flamethrower is a level down to me. Maybe things have been changed, I'm not sure, last time I used g5 it was weeks ago.