I see Liverpool being in the same city as a positive to be monetized/capitalized on rather than anything else. Everton can buy any billboard or magnify the presence of the club in any way they see fit through advertising like any business. The fact that we haven't isn't the fault of Liverpool FC. It's our own fault.
Liverpool being successful should push us to want to be a better team and club, and not just settle for what we have. One club cities tend to rest on their laurels a lot more as they know that they will have that fan base to hold on to. We don't have that luxury, being in the most contested football corridor on Earth with Liverpool, United and City on our doorstep. That creates problems as well as huge opportunities.
If Everton improve, we can create a huge rivalries with these teams and with Liverpool again, challenging right at the top. It will mean more TV money, more sponsorship money, and players wanting to be involved in these fixtures.
It is completely up to us to capitalize on it. These clubs will keep growing and will happily leave us behind if we don't raise our game.