Or... just or, they could have two entirely separate inventories: One for the “casual” modes which would give players a taste for the game and allow them to construct whatever cards/decks they may want to construct and another for when they want to transition to a more serious and competitive environment in which you…

Having an initial cost to a game where the only way to even get cards is to purchase with real money is not the smartest decision and the backlash they are getting is just and deserved. One of these two things can be true, but if you are going to gatekeep upon gatekeep in a card game then good luck retaining any…

Every other game - excluding literally every significant online CCG.  Do you even remember the post you were responding to?

Hearthstone: Free to play.
MtG: Arena: Free to play.
Gwent: Free to play.
Yu-Gi-Oh: Free to play.
Artifact: $20 up front to download the game.

You get the point now?