They can't and they won't.
https://www.rferl.org/a/ukraine-weapons-shells-european-unio...
https://www.dw.com/en/germany-ukraine-military-aid-2026/a-69...
Sending more munitions to Ukraine means it takes the Russian military longer to overcome the Ukrainian army by force of arms. The unstated aspect that is often glossed over is that this requires more and more Ukrainian men to be forced against their will to die for the territorial integrity of the country (because in 2024 the Ukrainian military is fueled overwhelming by conscription, not by volunteers). It's bizarre to me that is considered a "pro-Ukrainian" take. It's like egging on Paraguay during the War of the Triple Alliance to keep fighting, no matter if ~70% of your male population dies in the process. Just don't surrender!