Russian armies are already at the border with NATO in the Baltics.Your 'whataboutism' is misplaced.
As far as I can recall, there are NOT 'many writers here'--in this forum--who have expressed pro-NATO or pro-US positions on this war.
There might have been a few writers who did so. In this forum, the critics of Russia's war seem about as marginalized (at best)
as the supporters of Russia's war would be in almost all forums in the USA.
"Is Russia getting some more of the Donbass going to seriously weaken western Europe or US?"
That's disingenuous. Few Westerners care much about Donbas; most of them could not have located it on a map.
Western security concerns are about Russia's conquest of *all, or at least most*, of Ukraine.
(Russia's conquering all Ukraine may seem like a fantasy now, but it was a serious concern until recently.)
Obviously, a Russian conquest of all Ukraine would put Russian armies at the borders of NATO members.
Even a Russian conquest of all Ukraine east of the Dnieper (plus Kyiv or Odessa perhaps) could project Russian
military power significantly further westward.
If Russia and Ukraine can cut a deal whereby Russia gets some of Donbas, few Westerners will object that much,
apart from some rhetoric to reassure the Ukrainians that the West did not sell out their interests.
Ukraine clearly doesn't want to give up the Donbass which is why they were shelling them for 8 years. But Russia has a legitimate claim on Donbass too. Whose to say that Russian claim is less valid?