When its used correctly, I find item degradation systems to be terrific at forcing players out of their comfort zone, or challenging them to make hard decisions. When its slapped on for little or no reason, it becomes an out of place annoyance.
In my humble opinion, the item degradation system must to work in combination with other mechanics, such as those that rewards players for using specific items in specific circumstances. This encourages players to swap out their weapons/armour based on the situation, while still allowing them to fight through a situation if they don't have the ideal items. Strangely enough, "Pokemon" games do a terrific job of this with the most powerful moves being limited via a small amount of PP, which encourages diversity and specificity at the same time. Games like World of Warcraft use the degradation mechanic as a limiter on the number of attempts a player has at pieces of content. If you die too many times, you'll need to go back to town and repair, and allows the player to assess if they're capable of finishing. The mob respawn mechanic also plays in to this - if you bump into respawned mobs, your team is falling behind the pace the developers set. The two work together to give players indications as to their performance, and punishing their failure by subtracting currency from their inventory for repairs. Minecraft and other survival games also use the degradation system, in combination with their crafting systems. This forces players to continuously collect new resources while managing their current stockpile, which drives immersion and engagement.
In Fallout 3, the degradation system should have been a great way to encourage scrounging, adding to the immersion greatly. The execution was lacking, because a health bar on a weapon is very uninteresting. Having specific components on weapons wearing down while the gun is still usable, suffering specific performance penalties for each component, would have created more interesting gameplay. Using Fallout 4's crafting system, with each component having its own durability effecting its performance, would be interesting and easily understood. Of course, it would also be tedious to maintain across multiple weapons. Adding the extensive crafting system, giving players the motivation to scrounge through the wasteland, and removing durability was probably the best decision. Other games like Diablo 3 have the degradation mechanic, but it doesn't really offer anything. While it helps subtract gold from the online environment, the various crafting systems do a better and more rewarding job. Ultimately, I feel the durability system could be removed and no one would miss it. Not every game needs degradation.