Thanks for your reply. Yes, neither of those 2 points are surprising--the frustrations are (1) you can't get much more "core" in functionality than error-killing cell formulas and (2) people like me pay for Microsoft 365 in order to have capabilities on the supported products on the supported platforms. As for busy, yes I've done IT apps production support in a past life.
I did also reach out to an Excel MVP to see if a back-channel conversation to developers could help...