Card-Style Viewer:
I bought some card styles with the ingame gold currency and the blue orbs from the mastery and I didn't pay attention, so I missed the detail that it was just cosmetics. I then tried to add those “cards” to a deck and couldn't find them in my collection, for them being just cosmetics… Which was disappointing. :(
Without the actual cards included, those style purchases are basically useless in my opinion and I don't understand why you (WOC/MTGA) would make it this way.

Anyways, there seems to be no way to see which cosmetics have been unlocked.
I would like to ask to add a card style viewer to the collection viewer.
Plus a how-to-get-this-card option that points me to the required packs in the shop.

Better Bot-Play:
I would like to request more valid bot play options, because I don't like playing against other players. Because Magic is already a slow game and some people take felt ages to conclude their turns. Also, if you get attacked by like 10 or more creatures, the timeout timer runs down faster then you can optimize the blocking. The bot doesn't take long with its turns and allows me to take my time. Please more of that.
I think you are missing out on all the people that like Magic, but just don't want to play against other people.

And Sparky deserves some more dialogue variety while a match.

Apparently Boring Meta-Games 🤷‍♀️:
A friend of mine who is far far more competitive than me stopped playing some time ago this year. Don't know when they started, but I think it was also this year. They told me that they got bored, because in ranked games you will get to the point where the meta is either black-discard, red-rush or 4-Color...Something they said.
The background is, I wanted to add them as a friend in the game, now that I picked back up MTGA, but they told me they stopped playing for said reason… They are one of the biggest Magic nerds I know and they got fed up with MTGA.
Diagnosis: Lack of competitive meta-game deck diversity. …
I wonder if a deck diversity reward system sounds doable… or if it even makes sense.

Adding Friends:
Adding friends could be easier too. I think there should be a PVP-player history where the last 5 or so players I played against are listed. Maybe also for blocking some people too, for outside of Ranked, Event and Brawl.

Pity-Prices:
I mostly play YuGiOh Duel Links, and now in MTGA I realize how much I actually value the pity price system.
Because here in MTGA, a lost game = wasted time (Zero XP and/or coins), additionally to feeling bad for losing.

Accumulative Login-Rewards:
The login rewards in Duel Links are also neat. There you get tickets that allow one to pick a specific card from a list.
What if MTGA would give out wild cards like this, as an example, to reward loyalty as a nice side bonus?

But make it accumulative and not calendar based.
Because calendar based will become either a chore, or discouraging when it eventually resets!