The TLDR is they’re either set up for low intensity expeditionary warfare (Britain/ France) or the defence of their own territory (everyone else).
None have the capacity to send 500k soldiers to trench warfare in the Donbas or even operate in non-US led coalitions to the same purpose.
But Europe is not at war. It is Ukraine that is. But they need help with equipment, and balancing their budget. This is what they are asking for, nothing else.
Much fewer than 500k soldiers are needed for training Ukrainians.
Because a substantial number of Ukrainian soldiers need to be present across the Belorussian border and elsewhere in the country, the Russians have a meaningful manpower advantage on the frontlines.
But it’s incapable of providing alternatives to Starlink, Patriot or ATACMs. Especially not at the scale required to make a difference in Ukraine. The withdrawal of these systems would be disastrous for Ukraine.
ATAMCs could be somewhat mitigated with heavily increased medium range drone production.
The game of shooting down everything Russia sends was always a losing game. At some point you have to start addressing the source of the attacks - i.e. strike hard at the Russian infrastructure.
Starlink is where it would hurt though.