Any membership is only worth it if you actually use it enough to cover its membership fees, which isn’t hard to do with a lot of them. Good Sam, for example, is only $29/year, and you get 10% off their campground stays, a fuel discount at Flying J’s, propane discounts, and free dumping at Camping World locations. Just a few stays at one of their campgrounds and you’ve already got back the membership fee.
I would suggest doing a little research and finding the one (or ones) that you feel you will actually use and give it a try. I personally like the Good Sam membership. Here’s a breakdown of 7 of the big ones: https://camperfaqs.com/rv-memberships
Passport America is great if you can find places along your route, which typically isn’t hard. It’s more htan paid for itself for us. But just because it says 50% off doesn’t mean you’ll always get 50% off. Learned that the hard way. Sometimes you’ll only get it during certain seasons, or only during week days, and so on. Still more than worth it to me.
It basically comes down to your RV lifestyle. Ae you a full-timer or spend a lot of time in travelling in your RV? It’s likely going to be worth it. Even a couple stays at a harvest Host location will pay for the yearly membership. The best thing is you can try a few out for relatively cheap to see if they are right for you.