You have it backwards. It actually used to be the standard.
"Until the 18th century, the apostrophe was extensively used to indicate plural forms. Its use for indicating plural "possessive" forms was not standard before the middle of the 19th century."
https://en.wikipedia.org/wiki/Apostrophe
But in language, generally, usage can alter standards, so you may see a shift of grammarians saying it's acceptable if enough people see it as valid.