It's "avoid 'success at all costs'", which has _quite_ the different meaning.

Although, if the slogan has too high of a barrier to entry, I don't know what you'd think of the language itself.

No, it's meant as a warning against the trappings of explosive popularity. A language like C++/Java/JS is difficult to modify because of how entrenched the usage of the language becomes. In that sense avoiding "success at all costs" (which is how it should be parsed) allows "agile" development of the language.