While I do agree with the assessment that soulbound is close to web2, I don't think it has no place in a the game. I would disagree that (bot) extractors are killed, if an opportunity arises to extract people will take it. Printing cards indefinitely as rewards certainly is such an opportunity.

My bigger issue is with the value proposition for card ownership, because it is simply bad. Let's assume for a second you have reward cards and they are free to trade. The market will be flooded early because people know the price will go down and value loss is a self-fulfilling prophecy, because even people who want it know, that sell now and buy back in a few weeks will make money. Well technically it will transfer the money from however buys it.

Now let's look at the same proposition with unlock costs. Same thing, a race to the bottom. Especially with unlock costs reducing it is just a question of do I unlock now, because I think I will find someone who is ok with losing value or doesn't know better. In the end it is a dump, dump, dump because the value has to go down.

To an extent you have the same problem with card packs, buying them early for sure loses you value, because you know more will be bought and cards will get cheaper for that reason. Yes, eventually they may go out of print and value goes up but this is long term speculation at best.

I know, there are many more factors to card value than scarcity, but as you acknowledged scarcity strongly influences value. That is why I see limited print per card that is known from the start and not at the mercy of how the draws look like and how long the print lasts as the best option. While harder to realize for card packs with the burn and all that, for soulbound card unlocks it is rather simple to do. And if there are no surprises or unknowns, like how much will be played, how much will be drawn, how long is the set even in print, then the value proposition is much clearer. There will still be speculation of course and there are still other factors, but it is much better than the race to the unknown bottom we have now.