I’m looking to purchase a bike (probably second hand) and I want to make sure that it’ll be easily repairable in the future for at least standard maintenance stuff.
Thing is, I don’t know anything about bikes- I’ve heard people say off hand that modern bikes might perform better but are less maintanable, is this a thing? What qualities/features in a bike tell me that it’ll be easier to maintain in the long run?
AFAIK when people talk about modern bikes being less maintainable, what they mean is that there’s been sort of a proliferation of more proprietary parts (especially headsets and bottom brackets) in the last decade or so, along with a Gillette-razor-style arms race of increasing numbers of rear sprockets (with correspondingly narrower/more delicate chains). Frankly, it’s probably not that big a deal: you just have to get the right kind of tools to deal with the kind of parts you have, and replacements might be a little more expensive than if they were more standardized.
However, if you really want maximum ease of maintenance – or especially if you’re going to be, say, doing bicycle touring in some developing country where it’s hard to get fancy parts – IMO you can’t go wrong with a plain old threaded square-taper bottom bracket (don’t go so old-school that you end up with ashtabula, though), cup-and-cone threaded headset, 26" wheels, and a rear freewheel or cassette* with 8 sprockets or fewer (so you can use “normal” chains). Basically, all the stuff you’d find on an old '90s mountain bike.
(* I should probably have an opinion about freewheels vs. cassettes to go along with the rest of the opinions, but I don’t know enough.)