The game tells you what to do. If you're a new player and you don't listen when Shadowheart tells you to keep your distance, that's on you. The DM can't make it more clear how you should handle the fight than to have an NPC tell you to keep your distance.
And they could use this as a teachable moment. They could have more tool tips to guide you through this battle and use it to explain how to handle creatures with resistance and so forth.
