NATO countries/the West made it clear they don't have a vested interest in Ukraine. By virtue of that fact alone, it is not their war to fight. All the talk about a "swift" response from the U.S. is just that, talk. It's rather unfortunate for the Ukrainian people that they are being left to the wolves, but their sovereignty is their own business.
Access to the black sea is important to western interests.
Ignoring the above, western Ukraine borders NATO countries. If Russia were to invade Ukraine, there would be military action on NATO's doorstep, and there would be fear that Russia is not going to stop with invading Ukraine. If an invasion of Ukraine is seen as legitimate, there would be a legitimate reason for Russian military activity on the border of NATO countries.
Germany is soft on Russia because it is dependent on Russian energy. Plain and simple.