NATO is 1 billion strong hivemind with 10 times the military budget of Russia.
When was the last time such a big force attacked Russia with full force.
I know it's not gonna happen but regardless the point sticks that Russia problem has a permanent solution that no one is willing to implement no matter how much they shout and cry for Ukraine.
Also, this is not a direct war. this is a proxy war. Asking 'why doesn't the west go all-in vs Russia' is like asking 'why didn't America go all-in vs Russia in Afghanistan ? Why didn't China go all-in vs USA in vietnam war ?'
The answer is simple : In proxy wars, the puppetmasters do not want to get directly involved.
The main reason being, there is no incentive towards it - why risk your own troops and potentially a direct attack against your country, when you can let someone else do the dirty work ? Proxy wars also allow for carefully calliberated escalation/de-escalation ladders that you do not have in direct war. For eg, USA can (in theory) stop supporting Ukraine when it gets politically inconvinient for it. But if USA was directly at war, political inconvinience is not an option for de-escalation.
Proxy wars also allow for the ruling govt to have immense political manueverability & propaganda value.
And lastly the goals are what matters. Western goal isn't to conquer Russia. Its to degrade its military capability & spark a pro-western insurrection in Russia so the west can install another Yeltsin & rape Russian resources.
For this to happen, it must be a 'frog in a beaker with slowly raising the temperature, so the frog is cooked & the frog doesn't jump out' scenario. Russia must feel its 'futile' to continue this war and seek terms, Russia must not feel that its in existential threat, lest it escalates.
Russian goal is to delete Ukraine as a nation or at the very least, make it a rump state that is the Afghanistan of Europe & a permanent sore spot in Europe's underbelly, while weakening NATO alliance's overarching power- primarily its financial power, on which its military supremacy rests. Again, for this to happen, it cannot seek a quick victory in Ukraine ( lest the west realises trying to prop Ukraine is futile & quickly disengages, keeping its military hardwares intact and not adding to its debt to fund this war).
For the NATO, specifically US financial power to weaken, de-dollarisation must reach critical mass. For that to happen, a significant portion of the west's resources must be tied up 'somewhere else' than addressing the de-dollarisation push. That 'somewhere else' is Ukraine right now.
So to surmise, neither side seeks a quick victory, neither side wants a quick victory. Hence the trickle effect of arms and deployment from both sides.