Eh, you can pick plain white or blue button-up shirts with one of a few normal collar types and you won't be trendy but you also won't be "out of style". There are also some approaches to fashion the point of which is (at least in part) that they change only very slowly ("prep", for instance, which is practically defined by that quality—certain very casual styles like country/cowboy might also qualify, they have trends but you can definitely avoid them and achieve a look that's as close to timeless as it gets, on human-lifespan timescales).

Suits are slowly evolving fewer buttons but you're probably still OK with a 3-button in most contexts, and a 2 or 3-roll-2 is probably future-safe for 15 years at least. Suits may well be almost gone by the time they're out of fashion, really, and will only remain in contexts that don't really evolve (the 3-button is firmly OK in a legal, funeral, or wedding context, for instance, and likely to remain so pretty much indefinitely, provided, in the latter case, it's not an extremely formal wedding and/or you're not in the wedding party itself)

You're right that I don't care, but if you saw a photo of me in one you couldn't tell what decade it is from.

Classics never go out of style.