People are deluding themselves if they believe the cash shop will always remain "cosmetics only".
They WILL eventually add gameplay elements to it. I am willing to bet they still start with things like respec tokens in a couple seasons.
WoW added a cash shop with the promise of remaining cosmetics only, and then slowly added gameplay items over time to avoid a deluge of criticism. Overwatch 2 promised the MTX would only be cosmetic until they decided to wall off new heroes behind the battle pass. Sure you CAN get them without paying but the grind is designed to be so daunting that it pushes you to consider tye premium battle pass for the instant unlock.
D4's cash shop (and/or premium battle pass) WILL have more than cosmetics in the future.