Newer Garmins (including yours) have a neat feature where it will generate a random, round-trip route for you to follow. (This is a digression but bear with me.) I had an Edge 800 for almost a decade, it didn't have that feature, but, to basically get the same thing, I'd tell it to route me "back to start" and then just start riding in whatever direction the spirit would carry me. It was constantly rerouting, and I would mostly ignore it, but check before I decided to see what was down some road, to make sure I wasn't making a dumb mistake. When I'd start getting tired of it, I would follow whatever route it had at that point back to my home or car. This isn't a conventional way to use them, but it worked pretty well in practice.

You said on a recent 55 mile ride, you set a point on the map and it generated a route to get there, but not one you liked. What I'm suggesting is that you do that, but then start riding the way you'd prefer to go. Leave it in navigation mode and it will keep re-adjusting the route. At the point where you need it for directions, it will still know where you're going and where you are, and it will have a plan for how to get from A to B, it'll be ready to guide you.