Battle hardened vets are always helpful, having a squad of U.S. Marine vets with experience in urban combat would be good for any defensive forces, you don't need to train these guys, just guide them. These are probably welcome, and there are some vets from Special Forces operating in Ukraine already, there isn't much floating around about them precisely because they limit their digital footprint to the strictly necessary. Now, the volunteer retards who want to fight despite having no experience outside of a range? These are hindering the effort, nobody wants a Rambo wannabe giving their location away for some tiktoks lol!
If people feel like volunteering, and they lack combat experience, all they need to do is volunteer for humanitarian efforts. Delivering supplies to the frontlines, keeping civilians fed and clothed, are all efforts that are needed. But most of these guys who want to magdump shit and get medals without putting in an effort are too egotistical to do that and too stupid to help in combat, so they are literally useless outside of being meat shields!