The problem with the larger jobs is recovering from problems. The amateur gets deeper into the hole, the more experienced person can recover.
For example on a V6 cambelt, there are a variety of critical studs that can snap, on tensioners, covers and the waterpump. If you have a couple of jacks, then you can take the engine off its mounts and move it so you have better access to the snapped stud. You have right angled drills, oxy acetylene, possibly a MIG, and if all that fails, you have a big pack of timeserts to effect a proper repair. Jobs that are difficult, like removing the crank pulley, are easy because you have a 3/4" drive impact gun that can bang out 1000 ft/lb and will spin it off in an instant.
So yes, if everything goes well, the cambelt is indeed easy - but catastrophic if you get it wrong. If everything doesn't go well, then unless you are well equipped you have a very broken car on your drive.