I think it may be necessary to distinguish between people who want to learn what philosophy has found out so far, because they want to use it, and people who want also want to learn how to carry out philosophy, adding to the body of knowledge through participation in the published academic discourse.

Because, to do the latter:

(A) It may be helpful to observe at least some of the inner workings of the bootstrap process by which philosophy went from near totally wrong, to slightly less near totally wrong. There's a difference between learning a new recipe from a great cook, and learning the process by which that cook came up with the new recipe. In other words, at least some dead ends ought to be covered by the course, if only to help combat the feeling otherwise engendered "Oh, of course I'd recognise if I were going wrong. Why, the whole history of philosophy was an inevitable forwards progress to where I stand today, and I'm just continuing that."

and

(B) While it is false that there's nothing new under the sun, there are many many concepts that have already been proposed and discussed. If you don't cover them, then you invite time being wasted on reinventing the wheel, that could have been avoided if, at minimum, the people involved had been using familiar words and phrases from past philosophers that the others in the field would readily recognise. A necessary requirement for joining in and adding to the academic discourse is understanding and sharing the terminology, crediting each concept to the earliest person to come up with it. (modulo Stigler's law of eponymy)

Which isn't to say the balance should remain as it is. But neither should the baby be thrown out with the bathwater.