E: not just elastane but performance fabrics from athleisure in general, good moisture/odour/temperature control, easy to maintain etc. Some people like break in into their cotton/denim classics, but performance fabrics tend to not need break in in at all.
Other than that, good moisture and odor control, comfort/mobility of stretch too much of life upgrade. Also fairly wrinkle/iron free. I'd take convenience over durability anytime.
I will say synthetics haven't been able to replace bed sheets on most of criterias above.
I don't know if it's elastane but I've definitely seen QoL improvements in clothing compared to 35 years ago (back when I was a teenagers).
Underwear are soooo soft. And they fit perfectly. Same for t-shirts. Same for socks.
I don't know what makes some clothes so comfy (and requiring no ironing either btw) but there's "something" that makes lots of clothes simply better nowadays.
And they last too: I'm the kind of person who hates shopping (which drives my wife mad) so when I find something I like, I'll buy three or five of them (which drives my wife even madder). I've got some pieces I have since years and years (that one is nearly divorce reason ;) Sometimes I find a five years old picture and think: "Oh I already had that thing back then!?".
Yeah, many clothes are just simply better now.
That and having breakfast. It's the same almost everyday - unflavored whey + frozen fruits protein shake.
Brain cycles saved by not having to think.