I knew when I wrote it that sentence would get picked on, but I couldn't come up with a better way to phrase that. What I mean is: they can't do anything well. Any other character can outclass them. They suffer from the jack-of-all-trades problem something serious. Even taking all the things they can do into consideration, other classes can still outshine them in pretty much every way.
3 attacks at level 5 if you're dual wielding, or if two things are standing near each other and you're ranged and have horde breaker (or 4 attacks if you're dual wielding AND two things are standing near each other and you have horde breaker), all of which can add 1d6 to the damage from what is basically your only spell - yeah, that's pretty amazing! And then... that's it! As you said, other than conjure animal cheese and the occasional AoE (which any serious casting class would look at you and just say, "how cute," especially given your lack of spell slots), rangers just don't add anything. Sorry this is going sort of off-topic, but the most consistent praise I hear for the ranger is that they are great candidates for multiclassing. Anyway, just wanted to see if anyone with some high-level party tactical experience had any thoughts on a high-level straight-classed ranger. Sounds like no one has really given that a try.