Nice rant, but mostly wrong.
> Even ignoring the features that make it not so great a high-level language (such as the lack of a workable static semantics, forcing programmers to dynamically test what can be taken for granted in more civilized languages)
There are many more high-level features, than static semantics. Lisp is designed for runtime flexibility, not static semantics. Runtime flexibility allows lots of interesting high-level features.
> In the 80's, the only way one could reasonably hope to use Lisp as a systems language was to run it on hardware explicitly designed to run Lisp.
Lisp ran fine on five MIPS machines. Current systems have several hundred times the compute power.
The hardware was explicitly designed for Lisp in the late 70s when nothing comparable was available (single-user powerful workstations for AI/Math researchers developing large systems like Macsyma) and most development took place on time-shared mainframes with many users. The market that demanded this was a high-end market, thus the systems were developed, even though the were expensive.
Starting in the mid 80s, Common Lisp was moved to 1 to 10 MIPS workstations from SUN, SGI, Apollo, DEC, IBM, NeXT, Tectronix, and many others. The main problem at that time was that it would need 10 MByte RAM to run efficiently, which was expensive in the early 80s.
10 Mbyte. Today Lisp runs fine on an modern processor and some people tinker with Lisp-based operating systems, again.
> Of course, hardware support for features like dynamic typing and efficient dynamic allocation of lots of small objects doesn't come for free - this is what made Lisp machines expensive.
What made them expensive was the custom development for a small market, ten to twenty years ahead of their time. It was not the technology complexity of the hardware. People were buying future technology for lots of money, where comparable technology would appear 20 years later - the first Lisp Machines with object-oriented operating systems appeared in the late 70s for $100000 a piece.
Some of Lisp Machines used 8 bit ECC to provide error checking and correction, when memory wasn't that reliable. It made them even more expensive, because ECC memory was even more expensive than normal memory boards. With memory sizes from 4MB to 20MB.
Minor Lisp/Smalltalk support then went into the SPARC chips from SUN. Lisp ran quite well on those.
> dynamic typing and efficient dynamic allocation of lots of small objects
Every iPhone does that now, since Apple's Objective-C and the iOS frameworks are actually that: efficient dynamic allocation, of runtime-typed small and large objects.
If you want to see Lisp on a small machine, buy a Roomba cleaner.
http://www.irobot.com/For-the-Home/Vacuuming/Roomba.aspx
Their software was developed in Lisp already twenty years ago on tiniest hardware.
https://en.wikipedia.org/wiki/Roomba
L – A Common Lisp for Embedded Systems
https://www.cs.cmu.edu/~chuck/pubpg/luv95.pdf
It will clean your home, using Lisp on tiny hardware.