>>716509067
That's because Xen was only ever terrible in a vacuum. In the context of the game, Xen was a necessary capstone that tied the story together and fully showed off the intergalactic scale of it. The fact that Xen has a different feel to the gameplay and level design was to sell the idea of it being an alien world. Had it been longer - say, as long as BM's Xen - that might have been a problem, but it ends long before it gets frustrating and instead feels like the last desperate struggle to end the adventure. Without Xen, Half-Life would have been a worse game