I would argue that the goal is already accomplished by the fact that the event is effectively free entry provided you were willing to purchase a booster of Dominaria. Freeroll events are already not very punishing to losing; gambling does not need to be added on top of that as an incentive.

Providing an event that is inherently less attractive to experienced players with well tuned decks absolutely can't hurt the new player experience, and easing new guys into more competitive stuff gently is something that we should all be on board with.

I don't understand why you believe gambling is necessary to appeal to new players. Magic Online already has two separate leagues for each format, one with a prize structure that is less appealing to experienced players, as you say, because more of the prize payout goes to losing records rather than those who performed well. You are essentially using the (perfectly valid) logic for something else completely to justify the addition of gambling, without using any logic to defend gambling itself.