Arming people is of course not without its own problems. Apparently after arming civilians there has been a lot of shootouts between criminals. Or that is what some say. In times like these the truth can be hard to get hold of.
In Norway we got a sort of militia system like Switzerland. I was supposed to join after my military service. But of course such a system takes time to build up. You need systems in place to keep track of the guns, do semi-regular training etc.
Ukraine has as far as I understood focused on improving the quality of their normal military. But they have also been hampered by access to weapons.
Also Ukraine isn't that rich of a country. GDP per capita is lower than many countries in the Carribean. 3x lower than Russia per capita.
As for serving in the military I don't see the relevance that Obama, Clinton or Biden did not serve. They did no profile themselves as "though" guys and warmongers. Obama went on elections to get soldiers out of Iraq and Afganistan.
Clinton demonstrated against the Vietnam war. I have no problems with people not joining a war when they are opposed to war. Had I been a US citizens I would have fled to Canada for sure. Why should I participate in a war of aggression against a third world country?
In Vietnam, the US was playing much the same role as Russia is today. Just like Russian soldiers should lay down their weapons and desert, American soldiers should have done the same.
My point is rather that if you are the kind of guy who push for invasions and military actions then you should be consistent and live by your word. You are not doing that if you dodged the Vietnam draft.
I am close to a pacifist, but I still served in the military. And I did it despite hating everything about the military. There was enough to tough guys who found ways of escaping their service.
It is what pisses me off about guys like Trump. There is always some self-centered bully like that, but they always weasel themselves out of any kind of inconveniece or sacrifice.
However had serving meant invading another country and killing people half-way around the world, I would have no problem objecting as a pacifist or dodging the draft by going to Sweden or something. I don't think anybody has a duty to engage in a war of aggression.
Your duty is only to protect your own country.