In Ukraine, the Western powers actually helped the weaker side with weaponry, whilst in Palestine they helped the stronger side.
More than half a century has passed in Palestine since the invasion started. The situation in Palestine now is like if all Ukraine had been conquered with 80% of the Ukranian population living abroad and 2 small Ukranian enclaves were left surrounded by occupied Ukraine - one in Kyiv and one in Odessa - containing the remaining 20% of the Ukranian population in 1/100th of the territory previously occupied by the entire population.
Last but not least, as maybe the most shocking, is that the Russians are nowhere as racist towards the Ukranians as the Israelis are towards the Palestinians: Russia actually wants the Ukranians to stay in the occupied territories as long as they become Russians and obbey the Russian Government (to the point of activelly trying to force them to become Russians), whilst the Israelis want the Palestinians to either leave or die and are activelly against them becoming Israelian Citiziens. Israeli racism is so widespread, entrenched and endorsed at the highest level that the nation of Israel split their citizenship into Israeli Arab Citizenship and Israeli Jewish Citizienship and gave fewer rights to the former than to the latter: Israeli Law makes the fewer Palestinians who got Israeli Nationality (back when it was still possible) second class citizens, whilst Russian Law does no such thing for Ukranians in Russian occupied territories in Ukraine who become Russian Nationals.
There are 3 big differences in their situation: