You don't have to have that much power to drive 2160p, though.
The Radeon RX 6900 XT 16 GB is around 50-60% faster than your card, and by the end of the year there should be a new generation, that is supposed to offer up to 100% higher performance than that RX 6900 XT 16 GB.
You do when you want all the eye candy turned up with a frame rate near the max of the panel frequency. Also that may be true for the 6900XT and beyond but that's assuming you can get one, let alone at a price that isn't extortionate. "An item in your hand that's suitable is much better than a theoretical one"
On another note, I was in the market for a secondary to replace my FHD 24" screen as it's quite old tech at 60hz and only a 6 bit panel. But yesterday I 'overclocked' it to 75Hz, so I'm gonna keep hold of it until it dies.