Most of his technical problems would be non-issues if he abandoned portability to different CL implementations: Just pick a single implementation (SBCL) and use it. Other languages don't have this problem because there's only a single widely-used implementation.

Yet, a lot of Common Lisp developers keep kneecapping themselves by imposing the portability constraint where it makes absolutely no sense whatsoever: Few will actually care in practice about the 3-4 other CL implementations that the code happens to "support" (usually, entirely untested) but the code will be bloated by the use of 3rd party half-assed underdocumented "portability" libraries.

I'm a newcomer to Common Lisp and I do agree to a certain extent with the "social problems" part of the OP critique. If I had to emphasize one, it'd be the lack of focus and polish (which includes documentation) in people's output. There are very few people in the opensource CL community that consistently produce good code and that's a major problem.