One thing to always keep in mind is that your job can disappear very quickly.
If, or when, that happens those who've spent years in the comfort of that nice work-life balance and often, frankly, mediocrity (you don't improve yourself by staying in the comfort of such a job) are in for a shock.
Absolutely (with the qualification there are certainly comfortable jobs you can continuously advance your skills in), but the counter is that life disappears very quickly too, and if you have spent your whole energy and time prioritising your career you are in danger of finding a far greater shock when you are looking back on what is actually meaningful in your life.
If, or when, that happens those who've spent years in the comfort of that nice work-life balance and often, frankly, mediocrity (you don't improve yourself by staying in the comfort of such a job) are in for a shock.