If you wanted to let the new players know about Casual and Ranked battles and keep them from mistakenly playing Casual and losing, build a proper tutorial and let them know! I'm sure one is being built in light of the mobile launch, but removing a game to fix this is not the way to go.
Don't ruin it for the people who do know the difference and seek to play some casual to relax. I'd also like to test new decks from time to time without losing points and the only way to do it is to play Casual against real people. The AI Archas and Seasonal Events is NOT for testing out new decks. Its only by playing that you will find out whats missing or what needs to be changed.
Not all people play super competitively all the time. Sometimes, you want to meme around without causing harm to your points. I'm sure most people are semi-casual players who play to get better, make better decks and win - but not engage in any tourneys of any sort.
I love the game and love the devs more, but stop looking down on us and repeat what you did with the Midwinter patch.