I'm really not sure why you keep asserting that "there's profit to be had with mining" today

Simple. Miners spend X to mine and make Y, and currently Y > X. That's why most of them mine.

since in the system that Satoshi designed mining is a zero-sum game.

Do you know what any of those words mean? Mining is inflationary for the next 100+ years, by design. It is obviously not zero sum until block rewards are zero. Even then, it's not zero sum because the miners are doing work measured in hash/s and getting the reward of tx fees measured in BTC. You could argue this will reach an equilibrium, but "market equilibrium" is not the same as "zero sum game".

As long as some miners do better than others, the good miners will make a profit. Always. In the long run, if btc is more stable and/or after block rewards, that profit should be smaller.

Expecting regular users to mine because they don't want to buy on an exchange makes no sense. As long as there's a lot of money in mining, barriers to entry (like asics, server space, and cheap electricity) will prevent most average users from mining profitably or even at "break even" levels