I don't think we have that evidence for plastic (yet).
Also you totally can start buying plastic free clothes here and now. Just more expensive usually.
Not sure how socks used to be without plastic but pretty sure they'd fall apart fast.
Well, asbestos is a great insulator and lead makes beautiful bright paints, it's just that the downsides outweighed those great properties.
Or maybe (high strength successors to) Rayon, which as I understand should decompose like regular cotton.
And rayon doesn't exactly have a good history.
I'm all for looking for better things. Will be hard to replace some stuff, though.
You don't need lightweight waterproof clothing, you just like it. Getting a little sweaty under a non-breathable fabric or getting wet but staying insulated with wool will be just fine. Umbrellas are great as well.
What beats lightweight breathable fabric is not desecrating the planet.