If I am a miner, can't I create artificial scarcity by enforcing a soft limit? By simply not including transactions below my profitability threshold?
Sure, but you still have to validate, distribute, and store the large blocks of other miners. Also, full node operators that aren't miners will have no control over this soft-limit.
That's why it seems that the only working solution if we want to get a significant share of world's transactions, will be a system of relatively small number of full nodes, each of which is paid for its service somehow.
The disagreement seems to be whether we want a bigger share: should Bitcoin grow and gain more value by being more useful or forever stay at 7 TPS and be some sort of internal ledger for rich to settle their poker debts.
Your argument about rich vs poor is not completely honest, too. You still need
utility, otherwise you can each write your balance on a piece of paper and put it in your safe.
If Bitcoin doesn't grow, its utility will be forever fixed and limited. If you are a rich person, you probably want your money to be used, invested, etc. What good is a niche currency for you then? Just buy gold. If you can't do anything useful with your money anyway, gold is perfect.