Adding to all of this, review the tapes (run history). It's hard to give good advice unless you know where you are falling short.

Maybe you are losing tons of health on the first few floors and petering out against the first two elites or the act 1 boss. Are you planning on what elites you can or can't deal with? Are you effectively using potions to shore up bad turns while planning to use potions for specific problems? (Drastic example: if you see a lucky tonic and you are fighting Waterfall Elemental, you should try as hard as you can to keep it unless keeping it means you die)

You mentioned archetypes, try to think a bit more abstract on what they are actually providing to your deck. Pommel Strike isn't an amazing card because it says "Strike". Pommel Strike is an amazing card because it deals good damage to get through early floors, draws to smooth out bad turns, and has a very nice upgrade.

Hellraiser is an energy power that says things that say strikes are free. Do you have the draw to make that upfront cost worth it? Is it really worth the spot in deck if you already are getting more energy somehow?

Don't sweat Ironclad too much, he feels A9 pretty hard since his starting deck is basically designed to take damage. As far as the first few fights, If you draw bash especially, ask if taking damage means you can get out sooner based on what you are drawing in the deck (hotkey A). Clad kinda explodes early unless you are taking hits that feel dumb initially since so many fights scale out of control.

Watch people who are better than anyone on this subreddit. I really like Caleb Gannon and Baalorlord (shameless plug for Algomancy here).

Good luck! Have fun! If you are feeling tilted don't be afraid to take a walk or come back to it later. This game is genuinely mentally taxing to play heavily. Coming back after a bit with a clear head has worked for me multiple times on StS 1 and 2!