UI regression and old bugs
Brand new animations and display when opening a pack with Wilds of Eldraine. Its flashy and more in your face, but its just two rows. Its less intuitive to see where the uncommon and common split is. The dismiss cards button is a wash. No more accidental clicks before you're ready, but it's less convenient having the button all the way in the corner.
The deck collection filters removed the Standard/Alchemy/Historic titles. Why? Removing functionality? Not to mention now you have to guess where standard sets end and historic begin.
As for old bugs, ICR rewards used to very rarely not pop up (even though I could immediately go to my collection and see them listed as new about 50% of the time - though the other 50% I couldn't see them and had no idea what I got) And when opening packs, Rare cards half the time did not show if they were my first copy. Again, had to go to my collection for that and half the time they wouldn't be listed as new and I needed to manually search.
I figured these bugs would get better and eventually be fixed. It has just gotten worse. Now, ICRs almost never pop up. The dailies are the only rewards that pop up consistently. Rares from packs never tell me if they're first anymore. Going to my collection to see new cards is still at best a 50% bet, and may be lower now.
Overall, this entire update seems like a step back from a UI perspective.