If it's small, it's meaningless to the war outcome
I wouldn't say it's "meaningless". I've watched an interview with one of Polish volunteers fighting in Ukraine and he said that the presence of foreign volunteers boosts the morale of Ukrainian soldiers. They can see that Ukrainians and Ukraine aren't left alone in this. This helps. Furthermore, those volunteers are often experienced, ex-soldiers, including former special operators who can, for example, provide training to Ukrainian troops, thanks to which more Ukrainian soldiers may survive this war.
Also, I think that if it was so "meaningless" the RuSSian propaganda machine (including you) wouldn't be attacking those volunteers so viciously as some kind of "bloodthirsty, ruthless marcenaries who go to Ukraine, because they like killing people, etc." RuSSia wouldn't also try to scare them off by spreading the news that they're going to execute every foreign volunteer fighting for Ukraine. RuSSia clearly doesn't want them there :)
The title of stupidest belongs to foreign volunteers dying for Z
As I wrote already - the fact that Novichok doesn't understand something - it doesn't make it "stupid" :) Besides, I doubt that majority of them go there to "die". They go there to fight, and, as everyone, they hope they'll survive.
I also don't see you calling "stupid" mercenaries from Wagner Group who are fighting in Ukraine for money. You think they don't have families?