If the fee level is allowed to fall too low during some times, this would also probably again incentive behavior which will lead to more congestion in FOMO times. Runes or Ordinals could then practically be minted without any cost (and thus without a realistic "profit expectation"), as it occurred during the Litecoin and Dogecoin Ordinals waves (see
this graph) which were quite "useless" as they didn't really generate much value for their networks.
The higher incentives for data transactions is also the reason why I wrote that I have to think more about that proposal: perhaps even 0.1 sat/vbyte would already have these unintended consequences.
I agree that spam should be eliminated from Bitcoin. I think that the minrelaytxfee is not an effective tool for that. In fact, genuine monetary transactions are the most sensitive to fee levels while spam is not - as evident from blocks full of spam and the highest fees in the last 2 years.
For spam protection, there is the
datacarrier=0
which is much more effective. Also, there is the (OP_FALSE OP_IF) filter bugfix implemented in Bitcoin Knots.