For cases like strings as lists of chars and null-terminated strings, I think the reasons why they're generally considered mistakes is because the tradeoffs don

For cases like strings as lists of chars and null-terminated strings, I think the reasons why they're generally considered mistakes is because the tradeoffs don't make sense, at least not compared to their downsides. Null-terminated strings save a constant number of bytes, at the expense of expensive length-checking, potential complications, and liability for generating footgun mistakes (I believe they've been the cause of many a CVE over the years). Most systems aren't generally memory-starved enough that you can't spare the constant number of bytes for keeping track of string lengths. As for linked lists, I believe the times where they're more performant are fairly rare, and unlikely to occur at the level of a data structure for individual characters, which is reflected in String's poor performance in practice. Pretty much the only advantage you get from using string-as-a-list-of-chars is that you get to use List's Functor and Monad instances, but that probably should be avoided in any case.