> you’re very limited in the kind of logic you can express within a transaction safely

On the contrary, you have Lua which is much more expressive than SQL (yes Turing completeness, but there's a huge difference in how easy it is to read and understand).

> Pretending like redis is suitable for an RDMS workload because it executes things serially means you’re completely ignoring what transactions are actually used for and how they work.

Well the vast majority of RDMS workloads don't use serial isolation, that's part of my point. As for the rest, all I can say is I've worked on many systems in many industries and seen very few (honestly none) that actually made effective use of what transactions do and don't give you.