Go try get the P5 ssd for PC, oh wait you cant
Go build a PC with the same specs as a Series X for £450, oh wait you cant
There is nothing special about the PS5 SSD even if Sony is using it in their marketing spiel. They are buying the same SSDs everybody else is using. And yes, as of dec 2020, the fastest consumer SSD you can buy for PC is faster than the one used in PS5. The PS5 SSD being capable of 5,5 GB/s where as fastest consumer SSD for PC is already 7,0 GB/s. And yes, PCs can use compression as well, and they have had solutions for it years already. In few years the PC will start seeing SSDs with 16GB or even 20GB+ speeds.
And you are correct, you can't buy such PC now for that price, but you can buy one year from now. And you still get games cheaper. But that's not really the issue, the thing is that if you want best experience, you can't beat PC, it just costs more money upfront. As console generations are published so many years apart, they are obsolete years of their use time.
Day 1 they are perfectly good gaming platforms, day 700 they are obsolete by PC standards.
But it's not that simple overall. Horizon Zero Dawn, regardless of platform and technology was excellent game. Good games aren't dependent of being the latest and best technology there is. It's enough that the technology is good enough and the game itself is brilliant.
The case in Cyberpunk 2077 is bit different, as i doubt they will ever get it to work properly on the old gen consoles, but i'd expect it will be OK with PS5 and Series X.