Whilst it would be handy to have waypoints or an autoplan route (like native)
There is a reason it's like this... Quite simply - You need a plan (strategy) for your movement. You have to think of when you're next going to be able to log on and where you can get (safely) in the meantime. If your less active you have to take a slower safer route. If your very active you can keep changing direction to avoid obstacles making you faster.
This stops you from being able to trade by setting a pre-planed route and logging back on 3-4 days later to find you have arrived at your destination. It makes trading more dangerous.
Cliff locations are relatively scarce.. mainly in the center of the map (dhirim area you mentioned) and this stops you from being able to travel from one side of the map to the other in 1 click (along with rivers).
So I can see why this would annoy you (and many others) but hopefully you can see why they are beneficial to strat.
PS - I read on one thread that chadz made it so you
Slide along to reduce the likeliness of getting stuck.. With the amount of people you see on these cliffs and rivers this clearly doesn't work.. Was this from a previous strat and got removed or is it just buggy?? I think a sliding option would be better then making them passable (the speed reduction would have to be insane, such a thin line!)
Edit -
link for the slide thing Posted by Tomas... but chadz may have been the one to implement it, so i wont change the above