My issue with the tube isn't that it gets crowded. Of course it gets crowded; any subway system does.
My issue is that it always feels more crowded than it is due to smaller-than-normal trains and narrow platforms. I get that it's old and a lot of it can't be helped, but that doesn't mean it's not gross.
The trains themselves are grotesque sweat boxes, and the pricing, while bearable with an Oyster card, is ridiculous otherwise. Even with the card the costs are ridiculous when compared with systems in most (all?) other cities, which are also generally a much more pleasant experience.
Clearly, if you don't use an Oyster, you're mentally deficienct, but it's such an obvious, government-mandated tourist scam, and it's wrong.
Yes, it gets you where you want to go; it's a mass transit system. They all do; that's the point. It's still vile though.