I understand that it wasn't the right job for you on many levels and I am sorry about the apparently bad experience you've had. However, some of your points are specific to the type of operation you work/worked for and may look differently in other ones. For example, the lack of social contact with colleagues isn't necessarily a thing. It tends to be when you're flying for a large operator from your home base, there are many crews in the base and everyone goes about their own business in the downtime. However, there are also smaller outfits (with intrinsically lower job security) and charter/ACMI ops where you spend weeks away with the same bunch of people and eventually make friends (at the cost of spending far less time at home with your family). There's always a compromise somewhere. Where about said compromise should be largely depends on one's family status. While young and single colleagues enjoy living out of a suitcase and having fun with the crew on a day off somewhere far away, those who have partners and kids would happily trade this sort of interactions for more time with their families.
Many other downsides you mentioned can be mitigated one way or another. For example, why eat the poor quality airline food if you can bring a lunchbox instead? Dehydration to the point of ruining your kidneys or holding in for hours can also be mitigated in rather obvious ways. Not to mention that caffeine intake depends entirely on you. I've seen many pilots making themselves bottles of herbal tea with lemon instead of coffee for example. Nutrition routines depend more on you than on the job you're in. An obese pilot could have just as well been an obese accountant, especially bearing in mind that the pilot spends less hours per month sitting in a seat than a 40-hour-week office worker does in his office chair.