If the Glowforge cuts/scores/engraves properly on Proofgrade material, it is working as advertised. If it won’t cut other wood, the problem is the wood and or your settings. As for flasks and other materials, you have to test until you dial in your own settings. The whole point of Proofgrade material is that it is guaranteed to work with the provided settings. You do not have a paperweight, you are going to have to find settings that work with your non Proofgrade material or use Proofgrade materials. They are not out of stock.
Have you tried using one of the test templates to try to dial in your settings? Here is a good one that doesn’t use much material. New material cut test method