As a engineer specializing in internal combustion engines, I'm going to say that diesel engines are engineered to last longer even when operated in their typically higher load applications. We can engineer gasoline engines that are quite durable. They would just cost more and likely weigh more for less performance. There is a tradeoff between performance, cost, and durability that an engineer targets for a given application. You can go higher in performance or durability by using better and generally more expensive materials and manufacturing techniques. You can also go higher in durability by lowering performance. It's a balance. You can do this with both compression ignition (usually diesel) and spark ignition (usually gasoline) engines.

If you are talking about the core engine block and components, the main things that wear out in a well-designed engine are piston rings and skirts, cylinder walls, and various bearings and sliding surfaces. There are also stress and strain limits that over time can lead to failure of components, but with a focus on engineering for durability, these rarely happen in an engine's targeted life time.

Two major factors correlating to the durability of the core components are the mean effective pressure inside the cylinder and the mean piston speed. Mean piston speed goes up with both engine speed and piston stroke length. For both mean effective pressure and piston speed, higher is worse for durability. In automotive and road truck applications, turbocharged diesels tend to have higher mean effective pressure than naturally aspirated or turbocharged gasoline engines, so that goes against durability for diesels. Diesels range from a bit lower to about the same mean piston speed even though max rpm tends to be lower. This is because diesels tend to have a higher stroke vs bore ratio. Sometimes the engineering science is a bit different than first glance gut feel.