Your generalization at the end there sort of flies into the face of the whole "Expandable" card game genre.
Rotation loses players in every game, you just hope you'll make up at least as many new players than you lose old ones. They are alienated because the products they bought can't be used, or because their favorite things get cut, or because a rotation is just a clean time to stop keeping up since their current set is all legal together.
The argument here was not that we should be as big as Standard, but to indicate what other successful card games consider a full card pool. DTR deck building requires more cards, across different values, for the same variety of deckbuilding. I don't think we're there.
Core set had maybe one or two viable decks per faction. It was really, really boring well into the first cycle and pine box.
This isn't what I said. Retailers are not going to evangelize Doomtown, they already didn't do it or if they did they saw the game get cancelled in spite of their efforts.
New players aren't going to pick it up spontaneously because it's not going to get conspicuous retail shelf space, if it manages to get any at all.
What might happen is the current player base will continue to promote the game among their peers. Even your anecdote above has nothing to do with marketing or rotation, but word of mouth.
Also, $70 for a complete core playset is the cheapest expandable card game I can think of off the top of my head. DTR is $80 at MSRP, so was Star Wars. Netrunner, AGoT (1.0 and 2.0), L5R are all $120.