It's really as fun as it looks.
I think a lot has been said about this entry, so here's highlighting somethings you might not have noticed and why I think they showcase top tier gamedev behavior.
Yes, some blocks are just better than others, and yes you can reroll blocks. In the rush of the countdown clock, you might not have noticed though, you have a resource, gold! That's right, there is a maximum castle you can theoretically build, and no matter how quick you are on the reroll button, a minimum chance to get it!
That quickly evolves this game scope. Now, instead of binary best and worst strategy, we have the grey zone in the middle. "Making best with what you have". It's very very often overlooked in this competition and I think this tiny detail deserves heaps of attention. Are you really going to pray for the rare 3rd column king carpenter with two rolls on the clock, or just have him now?
On first glance, this is "just another countdown game". It's patently untrue here. The countdown isn't a loss condition, it's a scalar on the gameplay. It exists to encourage the player to make mistakes, and reward quick thinking, which elevates this above the usual "Do X in Y or you lose".
You've got a strong common consensus here that we'd like to see more content. No happier critique can you get. However, what I'd specifically want to see in content first, before new blocks (the easy road) is new challenges. Give me a reason to not always start the game with two walls in the bottom right. Give me an arial assault wave, or something to defend against with a warrior. You've put a seen amount of care into accessibility. The fast-forward mechanic is really well received until you let me click the little guys and have them go 'kwoo?' to entertain me.
I don't mind certain blocks and characters being worse off, IE, it's how we create the grey-zone gamespace to begin with, but even bad blocks could be buffed to work in say a rare comedy build.
I think the next obvious steps are to draw more playtime and mental rent out of the player. I can see a few strategies outside of a leaderboard, and I'm certain you've already been thinking through them yourself.
Outstanding work!