Economics - You are hunting for whales? But unable to meet their needs
https://youtu.be/atDH8vjN7U4?t=3836
Its interesting that you want so much for your product yet WotC does seem to have the right mindset. Like lets talk about the Mastery Pass, its a gem sink for the end user. Some will try to justify buying it but then find out they are losing $/gems for buying the Mastery.
In that the Mastery Pass should be a clear benefit. Make a 15usd/release (not worth any gems) pass that actually is GOOD. Players would be paying up to 60usd/year in this model which creates a nice baseline for each quarter. (another option is make a year pass which includes the 4 upgraded passes, plus value to justify a 90usd upfront pass. This brings in larger fish and smaller fisher to swim together, under WotC's hook.
Your goal is to incentives people to spend more upfront but also dangle the idea the product is only 15usd/quarter 'cheap'.
Lastly, integrate Secret Lair and MTGA. If I buy physical cards, those art styles should be available to me on MTGA. Ideally as I bought 1 SL=1 playset for MTGA. I'm buying the SL for something which has NOTHING to do with MTGA. Let me brag and show that I have this unique art and that I supported SL. You are not damaging SL but rather supporting it.
Honestly you can use a lot of help but don’t seem interested in taking that help for MTGA. Its kind of sad to see this app die in a burning glory (when I talk to paper players about MTGA, its like I was saying I belonged to the cult of scientology, which I'm not. MTGA could be amazing but so many players are annoyed with it. I think you can do better and choose to do nothing.)
(shame you are not paying for outside help. I'll take a percentage.)