Well what if the fees are not enough, or there are not enough volume tx going on, or anything else?
If the fees are not enough, it will be because there are not enough transactions to compete for the block space. In that case, the system will stop operating:
In a few decades when the reward gets too small, the transaction fee will become the main compensation for nodes. I'm sure that in 20 years there will either be very large transaction volume or no volume.
Perhaps at the protocol level, make it so that monetary transactions go first, then with less priority process non-monetary transactions.
This will have the following consequence: Ordinals will switch to another protocol, with transaction structure that is not biased by the Bitcoin protocol.
We should never censor or discourage any transaction that does not fit our description of Bitcoin, no matter what. The only objective factor that defines which transaction gets into the next block is the law of demand and supply.