I don't know if I can even blame the doctors for that. I mean, for a list of very generic and vague symptoms like that, there are probably thousands of viable d

I don't know if I can even blame the doctors for that. I mean, for a list of very generic and vague symptoms like that, there are probably thousands of viable diagnoses. Running every possible test to catch some rare disease every time someone comes in complaining that they "feel fatigued" would be completely unfeasible. Even if the cause is found, for many diseases the treatment is just "eat healthy and exercise". People think medicine is like fixing bugs in a code. Just a lot of tests, eventually a single cause is found, a pill is taken and the person is fixed. Reality seems to be closer to this: as you age, you accumulate damage everywhere. Eventually this damage is going to kill you, but before that it just makes you a bit slower and more tired. Sometimes, if you're lucky, some of this damage can be reversed, but mostly not.