One only need a web server to share gpx files really.
Planning routes can be easily done offline with desktop apps. Don't even start with mobile use, I have never seen a web based tool where you could plan a route by tapping on a smartphone screen without pulling your hair out of desperation.
Well, Komoot worked quite well for exactly that use case. I have also only very rarely found tools even in the desktop space that were quite as mature as Komoot for that use case.
Also the question remains, what do you navigate the planned routes / gpx traces? What happens if you notice you want to improvise and replan to hit some target on the way you saw in the distance while on the trail? This was (and currently still is) absolutely trivial and intuitive to do on Komoot. The best alternative I can think of is maybe brouter+ osmand, but that's really quite clunky in comparison with Komoot (similar to the experience you probably mean when talking about pulling your hair out)
Most people doing this on a regular basis do not use komoot on a smartphone anyway as the battery life of a smartphone with gps activated at all time is very short compared to a dedicated bicycle or hiking computer.
Planning routes can be easily done offline with desktop apps. Don't even start with mobile use, I have never seen a web based tool where you could plan a route by tapping on a smartphone screen without pulling your hair out of desperation.