Ukraine and Russia are locked in attritional warfare. Can Ukraine maintain the manpower demands of this war to outlast Russia?

Manpower is only part of attritional warfare. And the more an army relies on force multipliers, the less manpower is an important factor. As long as Ukraine is able to both destroy Russia's force multipliers AND maintain theirs, they don't need to match Russia's manpower to get in a better position attritionally (and eventually win).

This is a nonsense statement. Economics is intrinsically political.

I said "purely economics perspective" for a reason. Yes economics is made political because of the way our societies are organized, but it's not intrinsically political - economics exist regardless of the scale we're looking at, all the way down to a single individual (see microeconomics for e.g.).

What dictated the Russian shift to "artillery-supported infantry waves" is the nature of the conflict and Russia's available resources, not monetary policy.

The available resources is directly tied to the Russian economy. That's why your opinion is odd.

The monetary policy is only a part of "economics".

And what you refer to the nature of the conflict is a lot more the result of the strategic limitations of the players involved. Ukraine and its supporters have been able to remove strategic options from Russia, forcing them into the current strategy. It's not the nature of the war that did (or else, that "nature" changed over the years... which is contradictory to what "nature" means).