Much depends on the type of RVer that you are.
There is the weekend warrior staying in the same few CGs withing easy driving distance of home. This camper has no need of a directory. He knows his local CG, & sites, well.
There is the seasonal fulltimer. This one follows the seasons & has the favourite CGs to stop at as he migrates from summer to winter CGs.
There is the vacationer. This one has a few weeks a year, usually with family in tow, to get the best bang out of limited time. Price has importance but location & attractions will carry more weight in CG choice. Walmarts & such will do as quick overnights between home & a far away destination.
Then there is the longterm traveler. This is the RVer who is most likey an empty nester, retired, still calls a sticks & bricks home, but has plenty of time for travel. Trip duration is measured in months, not weeks. This is the one who most likely spends the most time using the most resources for finding CGs along the way. We fall into this group.
Trips are usually over 2 months duration, 3000 miles to 12,000 miles long & have a few events to be worked into it. In order of checking CGs RV Park Reviews is first stop. Check for Passport or GS discount (not a requirement). No on first 2? Check Allstays. It is rare that further looking is required beyond Allstays.
Booking what must be booked, while keeping some flexibility for time here & there takes some doing.