If MCP did not exist today, we wold not invent it.
We'd probably hormonize in basic conventions around json calls, and not much more.
The rest would just be api use / instructions.
LLMS to day are exceedingly good at calling RESTful APIs, the MCP standard provides little advantage.
The advantage of 'skills' is that they are more generic - an Enterprise LLM can evoke 'capabilities' which may or may not involved rpc type calls, and if they do, there will be varying level of instructions provided.
There's almost not point to MCP.