The role of racism (explicit and implicit) in zoning is undeniable. The problems modern zoning code 'solves' are rarely the ones that provide its legal justification. Zoning is inherently exclusionary, which has purpose in excluding incompatible uses, but the definition of which has been ratcheted up over times to sometimes absurd levels: a 'you shouldn't be able to see your neighbor house' sort of thing. Functionally, a lot of zoning code is written to pre-empt nuisance, and the level of pre-emption of expected/supposed nuisance can be extreme. Most zoning fixes are designed in response to solve new problems: how big the problem would actually have been beyond a single circumstance becomes moot. So it's easy for cities to become pre-emptively over-regulated. And as staff changes over, it's easy for the institutional memory of the basis for a zoning tweak to become lost, and zoning continues to operate on a 'not broke don't fix it' basis, despite the tremendous forgone benefits.