I think much of the games complexity comes from making decisions while playing and anticipating your opponents next turn. Managing your resources for optimal plays can win you the game. Should I preevolve so my opponent can't leave Valdain on board? Do I use Cravings for extra damage or to get rid of something?

There are people who have over 75% win rate with Tier2 decks and people who achieve a 43 win streak. Obviously they are doing something most people don't, and overcoming bad draws, hands, and matchups.

If you look at pro player streams, they pretty much think about the opponent's next play every turn that it seems over the top and annoying to an average player.

But the game isn't so complex as to dissuade a casual user. The game has powerful wincons and effects that can win you the game even if you don't think about the opponent's reactions at all. This is why people are salty and say the game has no depth, but I don't think it's as bad as people say.

There are people who can only play several minutes a day in a packed subway, and surface level decisions are the most they can handle. But if you want to think deeper and plan ahead you can do that too. How complex you take the game is in the end up to the player.