I'm the same way. In my opinion, if you've considered your options and thoroughly thought them through for months if not years, I would not say it is a rash decision.
Unfortunately the possibility to reject the shackles of society entirely is very low for me - it requires motivation, energy, and planning, but above all, a desire and a belief that things can change for the better. Maybe you can still do this - look into living off the grid, or alternative lifestyles (that can have a wide range of meanings, some more looked down upon than others but I simply mean outside the standard pattern society establishes and expects us to follow).
I hate to break it to you but this is mental illness. The thing about mental illness is that it's not something that always appears in some grand overt and clear fashion, it can (and often is) a subtle build that can crescendo into feeling like you need to take your own life.
In fact, what you're describing is potentially some of the most common mental health ailments out in the world today, you just don't see it.
Being dissatisfied with the status quo is not a mental illness in and of itself, although that is a feature many share - I suspect that to some extent, medicalising such dissatisfaction allows for easy containment of otherwise potential threats.
OP, what you're feeling is a sign that this iteration of life is not the one you were meant to live - there are so many other possibilities it is mindboggling. Even changing one variable can result in significant ripples or aftershocks years down the line. Metanoia discusses this more in detail - it's likely not your self you want to kill, but rather the aspects of your life that you don't find meaningful. Or as Marie Kondo would say, whatever doesn't spark joy.
