TL;DR the developers of slay the spire created a fun free card game within 3 weeks to explore and learn the Godot game engine. You can play it here: https://megacrit.itch.io/dancing-duelists
That's because it's not a product. It's an experiment for figuring out what they as a studio might be able to do with something new and untested. This is a trial run of a new engine, and they simply decided to publish the result for others to see.
This is more like publishing research findings than trying to market and sell something for a profit. Whether the result is good or bad, it's informative either way.
A comment the devs made on the steam announcement (under slay the spire) regarding someone being angry that this was prioritized over slay the spire 2:
Hi there, this is just a small, free game we made in a few weeks for a game jam in order to get acquainted with the engine that our next big game is currently being ported to. We figured our fans would be interested in knowing what we're up to as we work on our upcoming title since switching from Unity has extended its development time.
We're currently back to work on our next big game, this time refreshed and with lots of new tools under our belt! Hope people have a fun time trying this out if they'd like to!
So it's not like this is a big new genre for them, but it's also not meant to be a commercial for Godot.
To your edit, you doubled down hard in later posts, so I wouldn't say the hostility isn't completely undeserved.
I think you just really expected something different from what this was supposed to be, even when people explained to you exactly what it was supposed to be.