Might as well go big. 24 extra bytes per packet is not that big deal. And having that much extra space means you can screw up design multiple times and still be able to reuse lot of infra. Also getting rid of idea that you are even trying to manually manage the address space eases many things.
But it's not human readable anymore, nor backwards compatible. The expectation was that the industry is reasonable, but it proved to be as hard as it would be to push breaking email v2 implementation.
If you think v6 isn't backwards compatible then literally anything bigger than 32 bits will never count as backwards compatible for you. The whole point of making the address space bigger is to make it bigger, so what do you expect to achieve by complaining that the result is incompatible?
As a human, I've found that e.g. "fd00::53" is perfectly readable to me, and most of the time you're interacting with strings like "news.ycombinator.com" anyway which is identical to how it works in v4, so I'm not sure how far I'd agree with that part either.
