It's not complicated, I wore Doc Martens very long time and for some years they are no longer "Made in England" but manufactured in Mexico or Thailand. I have nothing against these countries but this is not at all the same quality. A simple example, my last "Doc" made in England I waxed once a week (with waxing old) is 10 years old and lives in the carrying 3 to 4 days every week ... While the "Mexican" pair lasted only 2-3 years and the pair "Thai" less than 2 years. So a loss of 70 to 80% of their lives for the same price as before ....
I do door for 3-4 more years because of the quality down and I do not feels good.