This is quite possibly the worst product made by a major company. It is simply unbelievable how bad it is. If it wasn't free to play, I wouldn't use it. And as it stands, there is no way I will ever spend money on it.

First off, the reward system actively discourages players from actually playing. Decreasing rewards as you play more throughout the day makes it so there is no reason to continue playing. But that's pretty innocuous. A similar minor gripe is that the animation in ranked play where your rank goes up down at the end of the game is painfully long. I need to move on to the next game, not wait while your unskippable garbage plays.

The main problem, however, is an issue I know you're aware of since so many players have, and continue to, complain about. YOUR MATCHMAKING IS BROKEN. To start, I will CONSTANTLY be matched against players several ranks higher than me, whereas I never play against those lower. Additionally, at least 4 out of every 5 games I will be on the draw. If it was random, it would be 50/50. It is not. I often play several dozens of games a day, and no matter the format, I get put on the draw. Even more frustrating is that I am always matched against decks that are stronger than me. I don't know what you have going on on the back end, but if I'm playing the top tier competitive deck, the one that wins literally every tournament in the format, which is the same deck I'm playing, I should be winning a majority of my games, right? Nope, I'll get 10+ losses in a row because I'm put on the draw against decks that have a favorable matchup against me. And don't get me started on the card draw. I play paper magic, so I know how shuffling works in reality. It is horrendous in this game. From having to run more lands than you ever would in real life in order to get them, to then drawing 4 lands in a row in a 20 land deck, ALWAYS getting horrible opening hands and having to mulligan just to be able to play? No, it doesn't work like that in real life. Sure, bad draws happen, but nowhere near as consistently as it does in game.

I am self-aware enough to realize that this comes off like I think someone at WoTC has it out to get me, and I know that's ridiculous. But when I get 10+ game losing streaks EVERY DAY (seriously, I count), there is clearly something wrong with the system. It doesn't matter the format, it doesn't matter what deck I use. It is broken.

So to recap:
Fix matchmaking. It clearly matches you based on the deck you're playing, and it constantly matches you outside your skill level. This needs to stop. If mono red is as popular as it is, why am I only seeing it every 10 games?
Fix the play order. Similar to how matchmaking obviously matches you based on your deck, it seems to do the same with the play order. I wouldn't get 4/5 games on the draw otherwise. But that's what I get. Every day. No matter how many games I play. Truly random would bear out to 50/50.
Fix the card draw. I don't know what system you have in place, but it is beyond broken and does not match reality. Again, the fact that everyone consistently runs more lands than in real life should be a sign. Bad draw happens, but not like this.

I'm about 4 seconds away from breaking my phone or laptop everytime I play Arena. I love the idea of playing MTG at any time without going anywhere, but the current product is horrendous.