Literally 80% of that game is a tutorial. It's not funny, it's boring. Truly a testament to Valve's shittiness. Easily the most overrated game dev of all time.

It was unlike almost any other game released up to that point. It's a masterpiece of game design because it's minimalist and they executed the atmosphere exceptionally well. Plus, it's one of the earliest "physics" based puzzle games that I can think of off the top of my head. As you said, OP, the humor definitely helped. The way the game plays with your emotions is simply masterful as well. I absolutely loved it. My dad doesn't play games at all but I sat him down and let him play this game and he absolutely loved it too. It's his favorite game and the conversations we had while he was playing it make it something truly special to me.