First that "plastic acme adapter" is not designed to form a seal and does not need anything more than gentle hand tightening. The seal is formed between the brass fittings inside the adapter and inside the propane tank. It takes a lot of excessive force and probably use of a wrench to break one.
The hose is a different issue. The problem is the deterioration of the hose due to exposure to propane. This includes drying out and becoming brittle. Another issue is that the deterioration can result in an oily sludge making its way to the regulator. This is not a quality issue but more an issue with the standard materials being used regardless of country of origin. I have been replacing my hoses approximately every 5 years due to becoming stiff and potentially cracking especially in cold weather. I am now trying a "non-leaching" propane pig tail. It is a little more expensive but should last longer. Several companies sell this. Mine is from Marshall Excelsior.