That’s all nice to hear. :)
If you’re fixing some stuff, I would start with the rubble, at least if taking it out is as easy as I imagine it.
Thoughts about thoughts:
Your ideas for turning it into skills sound good. Cooldowns and more upgrades could also be applied if you keep the concept of cards. It’s your choice what kind of game this should be.
If you want decks bigger than the amount of cards you draw each turn to be better, also consider different general mechanisms about cards. Maybe don’t discard the unused cards in your hand at the end of the turn. And/or draw less cards.
Having to look at and evaluate 5 new cards every turn in this kind of roguelike might be a bit too much. Card equip is just one of the ideas for that.
About smaller and effectively smaller levels: Considering that I often finish all my deckbuilding on the second level, these do sound like good ideas, if you keep the current game mechanisms.