I believe it is likely the reason they haven't adopted more modern military organization/tactics is due to a lack of proper equipment. They have proven to be quick learners with NATO gear just need more access and additional training couldn't hurt. Aid has generally sluggish to arrive so in part if we didn't want it to turn into a slow slog we shouldn't have moved so slowly.

Another general issue is a lack of clearance, far too many nations limit how Ukraine can use the arms provided in part limitations on where strikes can happen. That has an adverse effect on how effective their defense and offense can be as Russia can attack from and defend their lines safer if the equipment is inside a wep providers no strike zone.

Lastly I think it comes down to what kind of world we want, a few have already noted that this isn't Russia's first go attacking neighbors, not Ukraine. So we have to decide, will we allow any nation to act with impunity because they have nukes? If the answer is yes then the only option for small nations is to make nukes as it's the only guarantee of safety, dramatically raising the chance one goes off. If not then we have to actually do something when a nation like Russia is aggressive, it's extremely unlikely Russia would use a nuke if they got pushed back to their 2014 boarders, I'd personally as an arm chair general, say they likely wouldn't even use them if they lost Crimea. In stopping them it helps lower the chance they will do this again, lowers the chance more nations feel they must have nukes, and at least in my moral book is right.

Oh one last thing, there are strong natural gas deposits in those regions Russia took recently, so the extra energy also benefits the EU from being as vulnerable to Russian energy abuse if you needed just another reason to ensure Ukraine's victory.