I wear a few things still from the 80s: some karate trousers that come out every summer, some Doc Martens (although they're now relegated to odd jobs as I got paint on them which won't come off) and a wool jumper that's still the warmest piece of knitwear I own.
From the 90s/early noughties, I have some velvet flares, Gap Long n' Lean jeans, some M&S flat lace up ankle boots and a long denim skirt. However I've not worn these constantly over 30 years - they were stored away until quite recently.
I also still wear some vintage 1930s-1960s things that I've had for over 30 years but I'm not sure if they count as they're old enough to be immune to trends.
But generally, yes I do think that everything dates, including the so-called classics, e.g. even on a 'timeless' white shirt the shape and the collar and the general fit will change. However some things/styles do come back regularly and when they do, you sometimes forget they've ever been away - and that would be my definition of timeless.
As for what you can do about it - I try and put clothes away now when I'm bored with them, provided they're in good condition and still fit. And I no longer buy something because I think it'll be an investment because I've learned the hard way that that's mostly marketing talk.