This is referencing 'exa', of which eza is a fork. Exa was unmaintained for about a year before it was marked officially deprecated by the only person with write permissions on the repository.
It has definitely been long enough now since the forking, where not everyone is aware of exa, and this language/intent is now far less clear. I see you are not the only one to comment on this, so I think it's time to update the phrasing.
No the maintained here means it is a maintained (replacment) with reference that it is a fork of exa which was a ls replacment that is not maintained anymore. It does not say that ls is not maintained.
It's saying "modern, maintained", implying that ls is either not maintained (wrong), or ls is not modern (can be argued to be true). Only one of those two properties need to hold for the entire label to fit.
I strongly suspect the title could be translated into numerous languages verbatim, without losing the unintended interpretation. It is so for a few languages I know.
You can try it with translation tools.
The problem is semantic: in any language whatsoever (I suspect) if we express the idea that X is a replacement for Y, and in the same sentence mention some attributes of X, it means that those attributes are relevant to qualifying X as a replacement, which implies that those attributes are lacking or inadequately present in Y.
Without heaps of prior context, it is an impossible interpretation that the X attributes are not actually lacking in Y, but in a previously attempted replacement Z.
Absolutely nothing in the confusion here is specific to English.
I don't know why you would try to take this opportunity to criticize English when this misunderstanding could be present in literally every other language.
Because there is nothing whatsoever here that is a case of linguistic confusion or vagueness -- it is a conceptual issue of comparing two items, applying an adjective to one, and leaving the reader to wonder what that implies about the other item.
And no, English is not a "dumpster fire". Every language has its pros and cons. But there is no language on Earth that is a "dumpster fire". There is absolutely nothing productive or good that can come out of blanket, utterly unfounded statements like that.
The GNU Coreutils mailing list is fairly busy also.
This project seems to be using the word maintained for the meaning of actively developed.