4Game

My opinion ?
Sell the damn game. Obviously can't sell the rights because that would somehow contradict with the Witcher franchise, but sell the game none the less, with supervised character development, I don't know, some representative agreeing and watching over, maybe even suggesting character design based on the Witcher universe, and let that company to care take over and push this card game to the success it deserves.
Seeing it decline and the devs stopping the support for it it's just painful, while much shittier games out there get 10x times the player base. CDPR barely ever did any Ads for this game, or promotions. Never tried attracting new player base. I'm sure everyone who plays this game is just an auto swarm from the Witcher 3. You can't expect that player base to last forever. Appeal to the general public. Run ads on YouTube and other platforms like everyone else does, and finally hire a competent balancing and development team that keeps the player base in mind, and the health of the game, not just ways to make money.
A healthy game will bring in long term more money than silly broken card.