Librarian is a job requiring a masters degree. Library clerks don’t need formal training however. Bus drivers also require a CDL which I would argue also makes it skilled labor. I wouldn’t be surprised if street cleaners also need one.

But yes, many jobs are essential for our society that don’t require certifications, education, or formal training. Though I will say that some jobs are more necessary than others. There are both bullshit jobs and jobs where while the labor is real, the benefits of it to society are less than the value produced by it.