Which is harder, learning a language or getting a PhD?

getting a PhD in general only takes 4 to 5 years. (I am not including undergraduate years because nowadays almost everyone has to get a degree, so this is not extra time spent)

On the other hand, learning a new language usually takes more than 6 to 7 years to get to just C1 level. (remember C1 means being able to speak like a native in daily conversations). In fact a lot of people can't get to C2 no matter how long they've lived in a country or how hard they try.

It seems to me learning a new language is harder than getting a PhD.