Neither is tiny (therefore the supply is not per-determined)

Tiny as compared to the total supply, which it is (at least in terms of STEEM).

No, it is absolutely both.

I said it's both. But in the design of an economy that increases its monetary supply over time (like all real-world economies), they rely on growth to not have tremendous indvalidation of their currencies. This is exactly what hasn't happened here. Having a supply-increase rate of 7% yearly doesn't matter much, if demand for that currency increases faster. Every successful startup would show growth rates of above 50% yearly, and likewise most of these inflationary cryptoeconomies make such an assumption.

If the economy fails to grow as quickly as hoped / anticipated, price will go down. Obvisouly, STEEM was very hyped (much above its fair value) end of 2017, but there simply aren't enough drivers to motivate people (and I mean real people!) to start buying STEEM at a larger scale.

Seeing empty posts pushed to Trending multiple times a day will discourage anybody from buying STEEM ("This is what the stuff is good for?? Nah, thank you!"). Why not at least use this empty (but valuable) space to promote good Steem / crypto projects, curate great content or whatever. This is why I really don't get the appreciation both these projects receive.