Morris misses one reason for not getting involved: There is nothing we can really do about Putin taking eastern Ukraine - nothing unless we want to start a horrible war that might go nuclear.
This situation is quite different from the Chamberlain vs. Hitler 1938 situation. Back then France had a huge army on Germany’s border. The UK and France could have crushed Hitler had they chose so. Tragically, they chose not to.
But they mostly still had weapons and tactics from WWI. Once the Germans went around The Maginot Line, they were toast.
“Back then France had a huge army on Germany’s border”
Little good that did ...