To characterize their program is “fun” is a gross mischaracterization, and demonstrates a serious misunderstanding of the rigors involved in any technical/science/engineering PhD pursuit.
PhD programs are hard. They’re often lonely. They’re frustrating. They’re tedious. And there’s a tremendous amount of pressure. And it’s academia: highly bureaucratic and political and often unfair.
Unless you possess a serious passion for the subject, you’re unlikely to survive.
On the other hand, my friends getting the PhDs in subjects such as education (Stanford) and conservation biology (Mississippi State) have described it as the highlight of their life. After their first two years, they’re basically getting paid to do whatever they want. They audit classes. Apply to grants. Travel. And they write.