Definitely, no. But you can have both at the same time; in fact, in 90s-era applications and in professional desktop software, this is the norm. You build your discoverable UI, but ensure every action is attached to a keyboard shortcut, and that keyboard shortcut is also discoverable. Call it "progressive enhancement" of UI ergonomics, if you like; the point is not to put the ceiling for regular users on the level of your average first-time user.

> But learning is time consuming, too.

Not as much as time wasted if you don't provide a "faster path" to learn. I'm trying hard to understand, why modern UX designers react to the possibility (not even requirement) of users learning like devil to holy water. That is, beyond the obvious reason - pretty but useless software sells better, as you rate looks on first impression, but ergonomics on repeated use (i.e. after sale).