Sending weapons and money alone won't be enough to regain territories lost. Ukraine doesn't have the manpower on the ground.
That is quite possibly accurate so long as Putin is in power but that doesn't mean that weapons and money can't significantly influence the outcome of this conflict.
The Russian pull-out from Afghanistan was largely due to the lack of military success, the significant drain on the Russian economy as well as significant protests from the families of the estimated 15-26,000 Soviets killed and 54,000 wounded.
While Russia in 2024 is not the Soviet Union in 1989 many of the same factors still have the potential to influence the outcome of the Ukraine War.
The will of Russian soldiers to continue to fight may be impacted by their perceived success on the ground. If they feel they are winning the conflict then their moral may be buoyed. If they feel they are sacrificing their lives without any obvious victory in sight or if they feel their losses are too high for the minimal progress they are making then their willingness to fight may decrease which in turn could further reduce their effectiveness making them even less willing to sacrifice themselves. So while additional Western support may not result in a decisive Ukrainian victory and the recapture of all lost territories it could have a significant impact on whatever settlement does end up happening.
Same with the economy and the support of the civilian population. If the burdens of both continue to rise with little seen to be gained by the sacrifices the support of both the political elite and the general public for those leaders undertaking the war could lead to increased internal pressure to stop the fighting and even a willingness to give more in any negotiations. Continued Western support for Ukraine increases the chance for such outcomes.
Overall your sense of geopolitics seems to look more like a game of Risk than reality. This isn't a case of Russia (25 armies) attacks Ukraine (7 armies) so Russia wins. Conflicts are rarely so isolated especially in the modern, interconnected World. WW II wasn't a case of Germany vs Poland followed by Germany vs France, etc. It was Germany/Italy/Japan against a coalition of Allied powers fighting back against those fascist, expansionist states. Those Allied countries worked together to counter the expansion of the Axis countries because they knew (from the direct experience of Czechoslovakia, etc.) that unless they stood together in collective defence that they would be defeated individually.
The situation in Ukraine is the same today. The Russians/Soviets have shown that they are quite willing to pick off their neighbours one by one if we permit them:
- Ukrainian War of Independence (1917-1921)
- Kazakhstan Campaign (1917-1920)
- Finnish Civil War (1918)
- Sochi Conflict (1918-1919)
- Latvian War of Independence (1918-1920)
- Estonian War of Independence (1918-1920)
- Lithuanian-Soviet War (1918-1919)
- Georgian-Ossetian Conflict (1918-1920)
- Polish-Soviet War (1919-1921)
- Invasion of Azerbaijan (1920)
- Invasion of Armenia (1920)
- Invasion of Georgia (1921)
- Soviet intervention in Mongolia (1921)
- Urtatagai conflict w/Afghanistan (1925-1926)
- Sino-Soviet conflict (1929)
- Red Army intervention in Afghanistan (1929 & 1930)
- Soviet invasion of Xinjiang (1934)
- Soviet invasion of Poland (1939)
- Winter War w/Finland (1939-1940)
- Occupation and annexation of the Baltic States (1940)
- Soviet-Afgan War (1979-1989)
- South Ossetian War (1991-1992)
- War in Abkhazia (1992-1993)
- Transnistria War (1992)
- Tajikistani Civil War (1992-1997)
- Russo-Georgian War (2008)
- Invasion of Ukraine (2014-present)
These are just the conflicts where Russian/Soviet forces invaded their neighbours. It doesn't include the many, many uprisings within the Soviet Union against their brutal and oppressive rule/occupation or the very many overseas conflicts supported by the Soviets/Russians either directly or indirectly (including Syria, Mali, the CAR, Angola, Chad, Vietnam, Korea, etc., etc., etc.).
How long does the West sit back and let countries get picked off one by one until by the time they come for our territory there are no allies left that are able/willing to come to our collective defence?