[mprime1]

There's some serious flaws in your reasoning.

TCP guarantees order [as long as the connection is active] but it is far from being 'perfectly reliable'.

Example: sender sends, connection drops, sender has no idea whether the receiver received.

In other words, it works until it doesn't. The fact that sometimes it doesn't means it's not perfect.

TCP is a great tool but it doesn't violate the laws of physics. The 2 generals problems is and will always be impossible.

[acdha]

Yes, but the vast majority of network traffic these days is TCP and very, very rarely does that cause a problem because applications already need to have logic to handle failures which cannot be solved at the transport level. There is a meaningful difference between theoretically perfect and close enough to build even enormous systems with high availability.

[mprime1]

Rounding up 'usually works' to 'is reliable' is a recipe for building crappy systems.

Rounding down 'usually works' to 'it's not perfect and we need to handle edge cases' is how you build dependable systems.

Your first comment seemed very much in the first camp to me.