As a software developer I can say that it is not bad. It's pretty great, actually.
Doesnt mean the complaints about self-hosted arent valid, but "literally has to scale to the most insane volumes of data" and "is not good software" are two different things.
We're building a cloud service at the end of the day - its a lot easier to optimize a multi-tenant install than it is a single-tenant install, and that complexity shows up in the self-hosted repo. Can't really avoid it.