I have played some, now that AoT has been banned, but it just means the meta has shifted. In ranked (I am a Gold/Platinum player), it is all slow-roll planeswalker or control decks, with a rare RDW or Mutate thrown in. Companions are effectively dead after their errata change.
When T3feri is out, I will be significantly happier, M21 does not seem to be adding anything that is 'broken' yet.
I have not spent a penny on the game in almost a year, though. Just doing 4 Wins a day and the Daily quest (usually takes 30-45 minutes on Ladder, more around 20-25 in Brawl) gives me around 50-60,000 gold to spend on each expansion. They have been nerfing the Mastery Pass each new one, however. The first one, you bought it and if you maxed it, you earned a profit in gems. Second one, you broke even, most recent one, you come out at a loss in terms of gems. The M21 one is an even lower amount of gems rewarded, so eventually, you will have to 'buy' it using cash, rather than just earned gems, which is sort of their intent.