There is no reason to get defensive here.
So you do not believe that the protocol can last much longer than maybe a few years?
That's great but I feel that half of your arguments have nothing to do with that sentiment.
And to clarify things on the protocol level.
Bitcoin does something elegant that Lamport already proposed in 84 when talking about the consensus problem.
Cryptographically signed messages make solving the Byzantine generals problem easier because attackers can't forge the general's message
This is the basic building block for bitcoin.
Other consensus variants are better for other tasks (Like using a Total order multicast for a replicated state machine).
Sticking everything into one protocol makes absolutely no sense.
You bloat the system, the code gets messy and ultimately this can lead to major problems in the long run.
A slim protocol is a good thing in this respect. It is easier to maintain and better to understand
In my vision what stops bitcoin from going much further: a) Speed of increasing wealth concentration b) Deflationary system that prohibits price stability c) Inefficiency of mining where new resources are spent while the network doesn't gain in speed or security.
I find these properties to be core properties that are also highly flawed and beyond fixing.