There are two separate issues- the modem that your internet provider has supplied- in my case, a black box from Fibertel.
And your own additional wi-fi router.
I have used both apple airport and google mesh routers, and both work well.
But they are unable to work if you are not getting a good internet connection in the first place.
In my house, the problem is ALWAYS with fibertel, not my routers.
And there is nothing a different router will do about that.
As some people suggested, you may be able to use your phone, and not a hardwired internet connection- but that is usually more expensive.