except I wouldn't use the words "force legitimate users off-chain" and would favor "make microtransactions uneconomical".
That's a bad way of describing the problem, because it's not just "microtransactions" that are affected, and the result is not making them "uneconomical" - it's making them
impossible.
An effective block size limit doesn't mean that some transactions get more expensive - it means all the transactions which are allowd to be process become more expensive and the rest are prohibited entirely (right up until Bitcoin becomes so completely unfit for purpose that it's abandoned entirely)
Not impossible, uneconomical. A high fee microtransaction would be included.
Fees will still vary. I purposely left "microtransactions" undefined there.
Zero fee transactions still get into blocks today. Old coins still get preference.
What we would lose for sure in a scarcity market for transactions is the small TX with new coins, low fee, at high volume.