Greetings, and thanks to all those who answered.
As it turned out, the improvement brought on by disabling elementor was a red herring. Truth be told, searching for reasons in WP was a red herring.
I’ll leave the deatils for a long winter evening, however, the reason for the horrible perf. was xdebug. Yes, xdebug had been installed on the server but (and in my mind that’s a pretty big but) it was not enabled.
This means that libxdebug was being loaded in the server, but with all its functions disabled. It would look like that makes one pay (about) the cost of an additional test around funcalls or somesuch. Wrong. Installing the thing (in that environemnt, @least) means getting a 6-to-10x overhead on everything, including command line PHP (that’s how I found it, BTW). For the interested, it appears that the additional time is spent in making thousands og gettimeofday() syscalls, so it could be related to profiling (which is also off in .ini, for what’s worth – nothing, as it turns out).
Hopefully this will help someone else.
