Another tricky aspect to the game is that any given card may be great in one deck and terrible in another, to the point where taking it makes your deck worse. Strong players (such as jorbs, whom you can find on twitch) tend to lean very heavily on the card remove feature in order to get rid of bad cards.
There is definitely a luck component to the game but skilled players are pushing that boundary every day. Winning streaks on ascension 20 (the hardest difficulty level) are possible and always growing.
Funnily enough a really thin deck can also be a problem. If you have 15 cards and Nemesis adds 5 burns, you're in trouble without a way to handle that. Instead of thin or fat, the best way to think of it IMO is consistency (draw and exhaust help this).
I really like how each Act tests different strengths and exposes different weaknesses. A20 is tough but rewarding.
On lower ascensions you get far fewer status cards added, and if you're a new player you probably don't have act 4 unlocked.
There's definitely a lot of depth that you have to unlock over time. I sometimes watch Jorbs on YouTube as background noise and he'll often think over a single turn for 15 minutes or more. I don't have that patience.