I've read somewhere Feig was afraid the original cast would overshadow the new cast and he likes working only with women, who knows maybe they made it a gender swap reboot as a easy buck recognition off the name(which tends to be the motivation behind remakes and reboots)? and probably made them all women as a publicity stir or make it seem progressive(which seems to be a reason for gender swapping).

An all female cast would be fine if they were work colleagues or distant relatives of the OG cast but remaking the first film with women absolutely no point to that and when you have something as classic and icon as Ghostbusters you're out of your rocker thinking your gonna outdo the original with women.