> Somehow, this seems to be a fairly modern problem
With keyboards, yes, but gunk getting stuck in your mouse used to be a big problem, back when mice had balls. :)
Before even that, in PC towers and notebooks with active cooling, they used to be built without dust grates in front of the ventilation fans. The fans themselves used to gunk up!
The real “modern problem” is that you basically can’t clean a MacBook keyboard, since removing any key-cap has a 90% chance of permanently damaging the butterfly key-mech underneath. (I think the main improvement with the successive revisions of the butterfly key-mech is that they don’t snap their pegs off as easily when you remove the key-cap, so you can—in theory—clean them. If you’re a trained repair tech.)