Yes, the tutorial is not bad, and the 'Start Combat' is just right side the card. However please try to understand this from my perspective. I don't really play games that much recently, although in the past I have played Skyrim, Metal Gear Solid 5,etc., and also mobile games like PUBG. Have also played text games. I had no problem identifying buttons or such in any of these games, and that's the point I'm trying to make.
Just like how every website has it's own design pallete for buttons, links, cards, etc., making sure that every similar element looks the same, so should be for the UI of a game.
I think one of the following things may work:
1. Giving the text some background effect so it catches the player's attention.
2. Giving uniform styles to buttons throughout the game (or at least the tutorial).
TLDR; it's just me being dumb, but you can also use this feedback in a constructive way. I mean I've already typed such a long reply. Surely we can't let it go to waste, right?