Today's machines aren't CISC or RISC internally - they're ginormous out-of-order execution engines doing stuff that really can't be expressed in a linear machine language, and if there's an overhead for CISC, it's a tiny additional amount of real estate per core. Note that this is not a constant factor - as the rest of the CPU gets more complex, any CISC-related overhead becomes a smaller and smaller fraction of the whole. You can probably take the same set of execution units, forwarding paths, branch predictors, etc. and slap several different ISAs over it - I've seen CPU architects show experiments where (for x86 and ARM at least) two chips with the same number and type of these internal features will perform the same regardless of the instruction set.
There are a lot of factors involved other than the now-tiny technical advantage of RISC. There's a strong business incentive for the largest CPU design team in the world (i.e. Intel) to continue to produce x86 CPUs, rather than switching to another ISA. (for that matter, they tried once, with Itanic^H^H^HItanium, and it didn't work out so well)
Ecosystem effects mean that CPUs with non-dominant ISAs incur a bunch of various costs for their users, because everything from software through hardware just gets harder when you're not on the dominant commodity platform. (don't get me started on my experience with some POWER9 machines over the last few years...) A non-x86 CPU that's marginally faster/$ than an x86 isn't good enough - it needs to be substantially faster before it's worth the expense of switching, plus some more just to be sure that things won't swing the other way far enough to force you to switch back and pay that price all over again.
Most of the other observations in the post are spot-on, though...