I deal in vintage clothing and can tell you, the quality of the fabric and construction is so much better on older items. Even in “higher end” brands. For example, a Ralph Lauren jacket or sweater from the 1980s will be much better in every respect and wear better, than his products manufactured and purchased today.
People used to buy fewer garments of the best quality they could afford and then care for them with regular repair and cleaning etc. They would buy good leather shoes and have them resoled/stitched etc. at the cobblers. Many shoes and boots can not even be fixed, just thrown out. Shoemaking/cobbling is a dying skill.
Even tee shirts from anytime before the 2000s are heavier and thicker cotton and will stay nice for much longer. Plether/faux leather is ubiquitous and soon wears and peels and looks tatty. I sell real leather bags and many are very heavy sturdy leather and still look and wear well after 50 years or more, if they are cared for. Some have an aged in patina which is desirable to many people.
Many items in the thrift and secondhand shops now,are from the last 10 years or so and are the cheap,fast fashion stuff. So even the thrift world is suffering from this newer,poor quality stuff.
Buy the best quality you can afford in items and look after them. Buy vintage items,you can find unique items and also many classic and timeless pieces.