Yeah, I understand you on that point. I guess there will be no really end to this game in terms of how many cards get released. But I think the game will become more casual over time because several improvements to the overall gameplay haven't even been touched in discussions like. Guilds, DEC, Items, Spells, Skins, PVE and the option to purchase land or do crafting with items.
This game will become very versatile and awesome for every type of player (of course thats just in my mind) but we need to give the game more time to develop itself.
Any other Game that tries to achieve the same will also need a lot of time, patience and support from its community.
So Users who are leaving now never really had the interest to dig deeper into this game and "they" feel screwed because they had the wrong expectations from the beginning. I mean how can you feel screwed if you play the "daily Quest" and get "season rewards" after a while you sell your Deck for maybe 75% of its value. Most users would have made profit and had a good time playing the game for a short while.
They will come back when all this updates are in place...I guess. Lets cross fingers that SM gets the whole thing right until the end of the year!