Or doing a PhD.
After that, any non-academic job is super easy.
I don't know where/when those people you mention went to undergrad. When I went, it was brutal and endless. In order to graduate in 4 years, I had to take 18-20 credits per semester. When I wasn't in the classroom, I was in lab, and when I wasn't in lab, I was working on hours and hours of assignments. The professors never coordinated workload, so it all came at once in waves. All the exams were done in the same week, too, so you'd have to frantically cram. EDIT: Then, there was the job hunt during junior and senior years. Resume after resume, application after application, interview after interview. If I actually did any partying, I certainly don't remember it. Those four years were a blur of coursework that I still have nightmares about and am glad are firmly in the past. No job I've ever had in the decades since has come close to the amount of workload I had in university.
School was better. You don't become homeless if you get a D
Being told that as a child really fucked me up, actually. It's a really bad, pernicious idea.
For people who don't neccessarily like working (i.e. for most people), school and college are usually the best times of lifes. It's just that it's hard to appreciate that when you have no point of reference. My parents and aunt had this wisdom and, while I was a child, told me "enjoy yourself now, because it will be all downhill from here".