Mass conscription for what? The most dangerous bottleneck of western forces is supply of advanced weaponry, which is already taxed by the war in Ukraine. Even if these supply bottlenecks are fixed, it will continue to be a severe strain on public finances. And as you hint at, the draftees have to be trained to be more useful than being static targets. 21st century battlefields are very fast-paced and deadly and often asymmetric; all that stops an enemy from blowing up a target is air defense and missing knowledge about its precise location. The latter can be easily leaked by careless troops in a number of ways.
> 21st century battlefields are very fast-paced and deadly and often asymmetric;
The current battlefield in Ukraine is anything but fast-paced, and this is the largest continental war we’ve had since May ‘45 (the War in Korea has some shots of having been bigger, but then only for one year or so, 1950).
As you say, that's just the current phase of the war. No stalemate or operational lull holds forever. Anyways, that doesn't affect the rest of my argument.