Well, for Ukrainians it's pretty simple. When you're attacked, you defend. And usually it's not your choice that you got attacked....
As for Russians, it's not „Putin's war“. Russians got what they wanted for a long time. Many of those who are running today were happy with the war till it came banging at their door. Look at Russian history of the past 300 years. Many people over here do believe Russia is the exceptional saviour of whatever. Just look at ecstasy over annexing Crimea. Even opposition had to play along because saying anything against it would not be accepted by society at large.
Some Russians saw writing on the wall since 2008 or even earlier. Many left after 2014. The most optimist ones stuck till spring of this year... But there's no large enough mass of people to do anything and overthrow the regime :D
> no matter russian, ukranian or spanish, go get a weapon and contribute to the war
Ukrainians ain't „contributing to the war“. They're defending their home.
> Choosing for others, no, no and no. Never, ever. Over my dead body I would let someone send one of my relatives to a war because someone decided what is important or not for someone else.
Ultimately such is life. Going to war feels more personal, but others are guiding your life every day. And human societies built out precisely because of this group work. Individually, humans can't do much. Wether against nature or other humans who do organise. And neither other humans, nor nature doesn't care about your feelings.
But the bigger problem is when others' inaction prevents those who do want to intervene. Coming back to East vs West in europe. West was calling us „Rusophobes“ for years. Well, it turns out West was „Russophiles“ instead. Yet old line still holds and West seem to be holding East on a leash to not do too much against Russia. Because muh contributing to war... :( In other words, making choices for others.