The "motto" (if it can be called that) is not "avoid success", it's "avoid 'success at all costs'" which makes the sentiment clearer: increasing adoption should never be a priority over principled design.
Interestingly, the motto can be parsed two ways, with different connotations.
"Avoid (success at all costs)" or "(avoid success) at all costs."
Re:Go is Google's language, not ours
by stcredzero on Wednesday May 22, 2019 @02:34PM
(#19984084)
they want to ensure the language is never in a position where it's so important that certain behaviors or code be kept exactly the same because there's too much code that depends on it in the wild that they can't experiment with some new interesting feature in the next release.
Squeak Smalltalk had this. "Burn the diskpacks!"
[1]: Edited, thank you maxiepoo.