Except you don't get that it's not a meme, ideally CPU's were expected to scale into the 10-30Ghz range, that never happened because of the end of dennard scaling.
So yes ST performance is paramount, the only reason it's not is because CPU scaling hit a brick wall and because of power and leakage issues, when new materials become available that enable higher frequencies, you will see everything dramatically improve.
So no DX11 and Vulkan will not magically make all games faster, they are optimizations for graphics pipelines.
Most of today's games we're interested in run on 10year old machines just fine. If you think you can't run an i5 2500K /w a modern GPU and run 99% of all games you are clueless.
Most games are targeted at console specs and have held PC gaming back for decades.
The problem is game devs and engine makers don’t spend the effort to parallelize in the main loop everywhere they can.
You can get extra fps by having a faster single thread. Even still, if you had a 6 GHz single core CPU with a contemporary architecture then you would have an abysmal frame rate in a contemporary game. Those cores are used.