Examples of Western weapons that have been found wanting, and that were expected to be 'gamechangers':
Germany's Leopard 2 Tanks have been underwhelming in their achievements, and nowhere near as effective as proclaimed to be. And that's apart from the bad look of German Panzers crashing their way though the Ukrainian steppes in a replay of 1941. Just the thing to put a bit a steel in Russians' backbones.
Then there was the American Patriot air-defence system that couldn't even protect itself while expending 16 (or was it 32?) missiles. And the American HIMARS systems whose missiles routinely get intercepted
And we haven't heard much lately about the M777 artillery which were found to be very fragile when forced to 'shoot n scoot'. I've read somewhere that apparently the moving hooks are attached to the end of the barrel (!) instead of the wheeled-base and so causes stress on the still-hot barrels while towing during that shifting. And which routinely get taken out by Lancets.
Then there were the Turkish Bayraktars that were were so famous in the first weeks of the war. They are never heard about anymore, Thery just weren't up to the task.
And of course the anti-tank missiles which couldn't even punch a hole in the thin top armour of a tank when fired directly down on the tank from a bedroom window. And anyway, a lot of those had dead batteries too.
It's been said that Western weapons are designed to be profitable, and Russian weapons are designed to be effective. I'm rapidly being converted to that point of view. Tom Cruise and 'Top Gun' not withstanding.