How does it improve the language to be so top-heavy and chock-full of obscure unreadable arbitrary syntax, 95% of which nobody every uses, but that everyone still needs to memorize and understand in order to read?
That's exactly why Perl's philosophy of TMTOWTDI is intellectually bankrupt, and encourages write-only "creative snowflake" Perl code that's an inscrutable, unreadable, unmaintainable nightmare.
The language isn't any better for having $" as a shortcut for $LIST_SEPARATOR (or $LIST_SEPARATOR as a mnemonic for $", depending on how you look at it), because now you have to learn twice as many things, and all that duplicated effort and mental stress and syntactic surface area doesn't make it any more powerful or easy to use, has absolutely no tangible benefits, only pointless costs, and makes it twice as hard to learn and read and maintain Perl code.