Bitcoin is governed by the code people freely choose to run.
It's not that simple. Your oversimplification comes from one of the requirements of effective propaganda. Simple enough to be understood by the masses. What do they want? They want democracy, they want to feel they have the power. Tell them what they want to hear.
Bitcoin is not 'governed' by anyone.
The word 'governed' probably has the wrong connotations. Perhaps it is better to say that the "evolution of the network is decided by the code people
freely choose to run."
There is no block size limit--it is a shared dream from which we're now waking up from.
The current block size limit comes from the current consensus rules. Changing it requires creating a blockchain fork, like cloning bitcoin and hoping to kill the original.
Arguably, it is impossible to know with certainty what the current consensus rules are, other than by creating blocks and seeing if those blocks are accepted into the longest chain. We can't know for sure what code the economic majority is running--we could ask them or they could tell us--but they could lie. Proof-of-work is where we "put our money where our mouth is," as it were.