I don't think clothing quality has fallen. Quite the opposite. We are able to buy high quality clothing at a very low price. More advanced materials, more consistent construction, better construction, greater selection, etc.

Much of what you can buy today did not even exist 30 years ago. For example, trail running shoes more or less did not exist. Perhaps you could have had a pair custom made, at a high price, with the worse materials available at the time, but today you can them "off the shelf".

Even the many shirts I've received for free are very high quality and have endured years of abuse.