I have a few different perspectives on this. Most of my road trips have been in a Tesla, so I can draw very accurate comparisons to the Supercharger network. But I also have taken a long (1800 miles) road trip--an almost identical road trip to one I've taken a few times in the Tesla even--in my wife's ID.4, so I've had experience with non-Tesla networks (mostly EA) as well. I also track non-Tesla sites very closely as part of my
fastcharger.info project, so I'm familiar with the size and expansion rate of the other networks, as well as seeing their reliability as I check Plugshare entries of all sites that are added, removed, or updated.
The road trip we took was about 16 months ago, so a bit dated, but on that trip we visited 9 different sites (visiting one site twice). This was a mix of busy highway corridors and more rural chargers (including one lonely 24kW ChargePoint charger that apparently is no longer functional).
At no time were we unable to get a charge at all at any of the stops, and while there weren't a lot of alternatives, this may have been partly due to the fact that I had pre-researched our stops and planned for highest chances of success. Two of the stops, however, were much longer than they should have been (by about 45 minutes each). At the first stop (a 4 stall EA site), one of the stalls was out of order, and we pulled up and plugged into the last available stall. It would not give us more than about 50kW, however, so when another stall opened up, we tried to move to it, and things went a bit south. I think the system didn't recognize that we had unplugged from the first, and it took a 20-30 minute call with customer support to get the charge to start on the second stall! But we did eventually get it going. The second stop was also at a 4-stall EA site at an incredibly busy junction (Bedford, PA) with a queue of 3 cars ahead of us. We had to wait our turn and then had similar low speed issues with the stall we were on, but by then the site had pretty much emptied out so we were able to move to a different stall and continue our charge.
I will also note that due to lack of chargers at the time, we did have to divert about 30-45 minutes off the ideal route, however since then, there have been no fewer than 6 new sites added along key parts of the route that would have given us more options as well as avoiding the need for that diversion.
Due to my wife getting free EA charging with her VW, we had to use the app to initiate charging, and at some sites, a stall would show as UNAVAILABLE on the app, even though it was actually working. So this was a bit misleading. There were also several stalls that were down, although many of these were at sites that were not full, so there was no impact to us.
As for general reliability, my impression is that with generally smaller sites (4 stalls), one or two stations that are down wind up causing havoc since that represents a large share of the total site capacity. EA and EVgo tend to also shut down a whole site for upgrades which may take anywhere from several days to weeks. Obviously this would be a disaster in some areas if you show up to have the entire site down for maintenance.
EA had been on a pretty aggressive expansion until about 6 months ago and now it's slowed to a crawl. EVgo continues to expand at a good clip, but they are also pulling out of Walmarts around the country. ChargePoint continues to grow consistently, but I would say lower-quality sites many times at dealerships (and 24kW or 62.5kW chargers at that). Taken in whole, I would say the expansion of the CCS network is growing at least as fast as the Supercharger network, but again, not all of these are targeted at travel corridors, but more at dealerships and shopping centers.
I realize that everyone's specific situation and travel routes are going to experience a different perspective, but I hope this helps with the general case. I will say that I expect the situation to improve quite a bit in the next few years as the charge networks finally get a handle on what makes their reliability so poor, and more non-Tesla EVs on the road will spur further development of charging networks.