I have some old fabrics from the late 80s / early 90s (unused, which means I have UFOs that are 30 years old!), and some of them are thicker than my best fabrics from today but some are thinner. I have some recent purchases where the fabric quality was just terrible, and I don't think even the worst fabric from the 1980s was that poorly made. That's why I stick to LQS fabrics now, because some of the low-priced stuff is great, but a small fraction of it is nearly unusable, and I can't always tell until after I've bought it.
In general I'm happy with the quality of the fabrics available for quilting. I'm really impressed with the crispness and vibrancy of the dyes, and that's one of the things I really look for to differentiate fabrics.
As for quality of clothing these days ... I don't think it's even possible to buy 14oz-denim women's jeans any more, and that used to be standard. I am patching my old ones.