The ISS has regular enough operations required to dodge debris detected approaching for a near miss in space that I think it's definitely a concern for future operations.
Consider as well that stuff in orbit is going ~25,000km/h or more and at that speed even a small bolt would decimate a spacecraft on impact.
Just to follow up on the ISS, they have made a total of 20 avoidance maneuverers and they do it if they calculate the chance of hitting as greater than 1 in 10000.
So it is a thing, but I wouldn’t call < 1 per year regular
From what you can read on the Internet, yes it appears to really be a thing. Read up on Kessler Syndrome to understand a bit more on the subject.
The problem is not just about satellites, but random debris flying unpredictably on orbit. When there starts to be a critical number, the odds to hit something start to raise in the "very possible" territory.
The Wikipedia page for Kessler Syndrome even state that, currently, one satellite is destroyed every year by junk. That's only going to increase if nothing is done.
The issue is not in passing through the junk - that's like passing through the asteroid belt. We don't (or at least used to not) even plan a specific path through the asteroid belt, as the chance of hitting anything on the way through is so low.
The problem is if you want to stay in an orbit alongside the junk.
The dynamics of orbital mechanics are interesting, to say the least, but it in no way maps to the surface of some sphere.
A somewhat useful analogy is to imagine two circular racetracks, that intersect with each other in two spots. Each racetrack is like an 'orbit', and racecars going around them are satellites.
Make the racetracks really big, and put a car on each track. Have the cars drive around non-stop forever. The chance of them hitting each other on any lap is extremely small. However, if you let the cars go for a long time, and one of them completes a lap a little bit faster than the other, the times that they both cross the intersection will slowly get closer and closer together. Eventually, they will crash. If you put more cars on the track, the chance of two of them colliding increases. If everyone time they crash they create lots of baby cars, well you get Kessler Syndrome.
This is only a problem for these racetracks because they touch. We protect against this in the orbital world by keeping satellites in different orbits, that don't cross. The problem is that the orbits can shift over time due to gravitaional inconsitencies, and solar flares causing the atmosphere to bleed off into space, and the moon, etc. With lots of long lived satellites in low earth orbit, the chance for a crash increases. But even if we do get lots of baby satellites the other orbits farther out will remain useable (like geostationary orbits), you just have to be a little careful when crossing the low earth orbits on the way out.
If everything on a given orbit it going in the same general direction then their relative velocity is what matters. Collisions are not an issue at geosynchronous orbit for example.
