Have you done much traveling outside the country? Besides going south of the border to run cocaine, of course
Or mostly US NPs? Seems like you've been to every one.
I've been to Belize, the Turks and Caicos, the Dominican Republic and Honduras... and Mexico on cruises and we took a couple little road trips through a little of south-central Canada when I was a teenager...but that's it.
I hope to at least knock out all the full 47-50ish NPs (they've added a few in the last few years so I'm not sure the exact number) in the lower 48 before I croak..but I've only been to 23 (edit: 24, I forgot Mesa Verde...Edit #2: 25, I forgot that they've just turned Gateway Arch into a full NP in 2018 and we've been there twice since 2011) full NPs so far, so I still have over half of them to go.
We have also been to a ton of the top State Parks in the states we have visited, and a ton of the National Monuments, NRRAs, National Battlefields, National Sea-lakeshore and National Historic parks which are in the NPS system...and a lot of the popular National Forest sites which are in the NFS system...which are highly underrated and underfinaced imo.
We are going to 4 new countries on a 10 day cruise we are taking in November...Costa Rica, Panama, Cayman Islands and Cartagena Columbia...so I will be able to say I've been to another continent.
Ps: IMO...Gateway Arch, while really cool, and while I think everyone should check it and the museums on-site out...should not be a full NP..
There are several AWESOME scenic areas among our federal lands that should have been made a full NP before that place.