A constant annoyance is having to stop what you’re doing, find someplace to sit down, take off your shoes and dump whatever bits of dirt, gravel or whatever has insinuated into a place seemingly calculated to cause the most discomfort.
I used to hike with gaiters, which wrap around your shoes and block stuff from falling inside, but they retain heat, add weight and make my feet sweat. I’ve found out that hiking in long pants serves the same purpose most of the time.
I’ve often seen trail runners wearing very tight-fitting, stretch-fabric gaiters — which looks like a good idea, but keep in mind the anti-crud mandate is munch stronger for runners, who are even more loath to stop what they’re doing and much more vulnerable to the blistering consequences of not stopping when there’s a pebble in there. They need those gaiters much more than hikers do.
Still, taking care to reduce your crud encounters will make your hiking much happier.