m4 did in fact use left and right quotes from the beginning, but it still had other quoting problems. Really terrible ones, to the point of making the language unusably bug-prone for anything beyond very basic tasks, which is why it's mostly forgotten.

No, because it's missing semantic information carried by the distinction. The ’ at the beginning of

    ’Tis brillig, and the slithy toves

is not a left quote ‘ but an apostrophe ’, like the apostrophe in “can’t”; but ‘tis certainly possible that someone might want to put single quotes around a phrase beginning with the word “tis”, such as the Latin ‘tis misereri’. By contrast to “can’t”, the ‘ in “Hawai’i” is the ’okina used to represent the glottal-stop sound in the Hawai’ian language, not an apostrophe.

" and ' are themselves conjoined with other uses.

" can be inches or arcseconds from cartography.

' can be feet (of measure) or arcminutes from cartography.

These actually all have slightly different symbols, and the symbols for the left/right quotation marks are actually farthest from this approximation, even if they are the most frequent usage.

It’s always been wrong in some respect to use a single available symbol to emulate three or more different typographical tasks, but quotation marks may actually be the one where the emulation is the most wrong.

That equivalency only holds if there is a visual distinction in the output between the l and the 1. There often wasn't when this practice was popular.