I did this recently at home (saves money after owning it for a year, as it's "paid off" then in monthly modem rental fees), and although I have problems with the level of control my ISP has over the modem (there's no configurations or login, you activate it on their network and they control it fully), it's now just a "dumb modem" and does nothing else.
Then you knowingly bought a combo shitbox. There have always been quality consumer wireless access points, modems, and routers available, but you chose to buy the combo shitbox.
I did this recently at home (saves money after owning it for a year, as it's "paid off" then in monthly modem rental fees), and although I have problems with the level of control my ISP has over the modem (there's no configurations or login, you activate it on their network and they control it fully), it's now just a "dumb modem" and does nothing else.