There is a really obvious one, and it continually bothers me because it's right near me, but even objectively, it is several years overdue, because there is no decent alternative route. Anything else adds 3-4 hours to the drive. If anyone is needing to drive between the San Francisco Bay area and Boise, ID, there is one route that everyone takes. You drive I-80 East from California into Nevada, past Reno, until you get to Winnemucca. And then you turn onto U.S. federal highway 95 to drive North up to Boise. That gap from Winnemucca to Boise is over 250 miles! It has two sites with CCS and CHAdeMO, but either or both are frequently broken. There is no Supercharger at all, and not even any pin on Tesla's future maps showing they plan to put one there.
Yup, that's one of the gaps. I have driven it in ICE. In my Tesla I would probably pause for an hour at the RV park if I had to going north because the CCS was down.
Now, in general, I think it's fine to fill gaps with CCS as long as they are reliable. I would rather Tesla put new chargers on routes where there is nothing. Or failing that, one of the CCS/CdM networks. Most effort seems to be going into charging on interstates and in cities, and yes, that's where the most volume of cars will be found, but that's not the only factor to consider. To me, I like there to be no compromises to owning an EV, and the dead zones in the map are high on the list of compromises. Get rid of more of those zones and you start telling EV buyers, "You can go (almost) everywhere" rather than "As long as you stick to the main roads, road trips are not a problem." The latter was a great first effort, but unless those stations are getting lines, let's get those unusual roads. It doesn't have to be 8-plexes. It can even be just a 2-plex of 50kw. It can even, in some cases, be a station with a built in battery that can only charge a few cars/day (though in that case you want to reserve it, this is definitely not a first choice but it's workable if you have a place where you can't pull 100kw.)
But I hope for the day when there's no good road trip I can't take without much thought, including the side trips. Much more than I long for drives on the interstate. Or even enabling those who can't charge at home to charge in cities. I feel for them, but the right answer is to get more L2 charging in rental housing lots and offices. Not more EV poor imitations of gas stations.
Perversely, on these road trip routes, you have to space them a bit closer. If I am just charging down the interstate, I can have them 200 miles apart. On a wander in rural country, I want to be able to backtrack and take side roads.
Two of my top ones are the route through the national parks in Utah, which is perhaps the best drive in the lower 48. No fast charging on it. The icefields parkway, which is perhaps the best in the continent, could still use more though they just added a supercharger in Jasper. A lot of national parks need more, like Crater Lake and others one could name. Those would not actually be low volume use if they were there. Indeed, since people stop for a while at national parks, having lots of ports with lower wattage is actually the best plan, since when you stop there for 4 hours you can't go to move your car.