But that breaks the layering (where reachability is provided by l3 and transport by l4). Now existing internetwork routers cannot handle your new 144-bit address format.

The folks at IETF meetings are doing a wonderful job trying to keep existing tech working. That's why you always extend old standards and rarely deprecate anything. Just look at BGP, for example.

We, the application software programmers on layers 5 through 7 with the "move fast and break things" attitude, could not ever have designed anything like the internet and keep it running as long as our current one has been.