What's a job most people deem as "easy" but isnt?

Teaching
- Oh do I ever hear this one. Sixteen years I did that. Between the spoiled kids, their even worse parents, and the administrators who only see opportunities for more cash the good ones were barely enough to keep me going.
  And when the number of good ones started to drop, I had to pull out.
  
  We're struggling with that so much right now! New admin has chased away everyone who was old enough to retire or good enough to go somewhere else. Now we have new people in every position who are trying to reinvent the wheel and failing miserably.

I think a lot of people view farmers as stupid or the job as simple. I'm a software engineer who also started farming and there's a lot more to things than I think many realize.
- Few individual farming tasks are not simple, but there are so many of them that it gets comicated really fast, just like most things that humans do. My hot take: Farming, as opposed to most of those "complicated" tasks has been around long enough for humans to automatically divide it into tasks without actually thinking about it.
  
  Maintaining soil fertility, crop rotations based on nutrient usage, etc. are things most don't think or know about. Even when to and how to turn seeds into food is more complicated (or can be, at least, to do it efficiently) than I think most consider. Edit: also forgot avoiding planting certain things in the same area that are succeptable to the same diseases in following seasons.
  It is, as you point out, a lot of breaking down and scheduling tasks with multi-year planning (at least for my scale for rotations and fertility) which is probably why, as an engineer, I kinda dig it.
- I'm an industrial-IT-meets-offshore-technician-thing, and my dad was a dairy farmer. He could never have done what I do. But I could never have done what he did either.
  Being a farmer is like a handy man on steroids. Upkeep of buildings and machinery, building new where appropriate, caring for livestock, bus8ness finance/book keeping, ground water drainage/management, et al. And on top of that he was a semi-professional footballer on the side.
  
  Yeah, I'm not even close to ready for animals yet, heh. Probably starting in 2026 or 2027 we'll get chickens, but getting a farmsitter for when we want to go on vacation is a concern
- It is very common for people who work in white collar fields to have incorrect opinions about jobs they have never worked, yes.
  
  I would suggest blue collar workers aren't immune to that.

Fast food. The job itself is easy, like the steps are the same and repeatable, but I've never worked so hard in my entire life. "It's just flipping burgers" yeah well it's a burger every few seconds. It's the pace at which you make the burgers, burning yourself with hot fries, making the stupid ice cream. All while poorly trained managers tell at you for putting 3 instead of 2 pickles on hamburger.

Chambermaid or cleaner. You never work as hard as you do in those jobs!

Going to throw a curveball. Networking.
Sitting on my ass all day is easy. But if I make the smallest mistake, it gets quantified very quickly and everyone knows about it.

Being a mom. I'm not even one yet and simply help a certain family au pair style, and the childcare part is like a balancing act fueled by attentive dedication and no room to screw up badly. I actually help with teaching, and that's easier than getting out of that line of work to spend time with just two of the kids that show up.

Almost any kind of manual labor. It's simple (as in not complicated) work, but still fucking hard.

Delivering the mail
- Really? How come?
  
  You have to wait until the truck with mail comes from the hub, so it doesn't matter how early you come into the post office. Sometimes the truck will arrive at 5:00 p.m., that means you have to sit there and spend an hour and a half to two hours case in your mail and parcels.
  Then you've got to pull all that mail that you cased, into trays stack it up and then you have to stalk your truck and then do the same with the packages.
  Then you leave to the route at about 6:30 to 7:00 and you've got about 3 hours left to deliver mail and packages. You've also got to deliver the mail under any weather condition.
  Lastly most carriers don't have their own route. They run the routes of the carriers who take a day off so you're constantly doing different routes every day and you don't know them so it takes you even longer to do your job because you have to learn the route.
  It's a stressful job.
  One lady told me, "You're not broken in yet until you cry"

There are different ways that a job can be difficult. Some are physically demanding. Some require a lot of skill (and/or luck). Others can be psychologically challenging. Some are a combination of those and more.
I used to work in retail customer service. Honestly, I saw it suck the life and happiness out of some of my coworkers. People would have breakdowns or turn to drugs and alcohol. One of the reasons I was able to handle it is because I knew it wasn't life long career for me, it was just a job to support myself while I was in school but it left me with a lot of anxiety and maybe, to some degree, PTSD or something similar.
There are a lot of responsibilities and expectations for that type of job. I had to manage the front-end staff. Make sure folks showed up for work, got out on time, got their breaks, performed their duties, make sure they were safe. That was a job in and of itself. I also had to count money, checks, run reports, and a bunch of general office / accounting duties. And then on top of all that, any time there was a problem, I was the first in line to have to deal with it. So, a large number of my customer interactions were with unhappy people. Way too many angry people who are rude, disrespectful, lack empathy, and are so demanding. Lots of ungrateful people and lots of scammers.
The icing on the cake is that the schedule is highly irregular and the pay is crappy.
Really, a customer service job like that is a lot of exposure to a lot of bad people and a lot of horrible behavior. It can be exhausting and mentally damaging. More than most people might realize.

Janitorial