Some solid points there. I think a lot of this really depends on where you are in your Frontier journey.

Once you’ve more or less maxed out the set, it does turn into a bit of rock-paper-scissors, I agree. But that’s also the stage where players are expected to slowly transition toward Modern. Collecting extra copies and selling them to fund a Modern-style collection feels totally fine to me.

Frontier cards are (and will be) heavily overprinted, and honestly, that’s a good thing for this set. Prices become very cheap, and while selling cards won’t give you a huge boost, it does provide small, steady funding to move into Modern. Nothing game-changing, but that’s okay in my opinion.

Note 1: You still need a spellbook to sell, so that already means a player has converted.
Note 2: I agree it would be great to see actual conversion-rate data. My guess is it’s still on the low side, but the team is clearly working on improving that, and in this market, that’s not an easy task.

As for “usual players” spending time in Frontier: I still see that as a win. Keeping existing players actively engaged in any format is better than passively playing land or just botting in Wild. Engagement is engagement, and that matters.