I believe it depends on how you look at work. The higher you climb the career ladder the more responsibilities you get. Everyday is an opportunity to make some progress — get something done, move forward, show up and make progress. Some days you are at the best of your mental capacity and some days you are not. It’s important to recognize those days and focus on low hanging fruits on low mental capacity days vs getting high value work done on good days. Managing yourself is a part of your job that’s not in the job description.
As a professional, it’s my responsibility to get my part done and make progress everyday. Things add up over long time. Similarly not getting work done does the opposite, let’s lot of backlog pile up.
If slacking is the result of procrastination or lack of attention or lack of motivation, I recommend people get help.
Imagine calling customer service rep and they just work 5 hours a week and imagine them responding to your requests a week or month from now. Imagine everyone working like this, society won’t function. Not doing your part for what you’re getting paid for seems unethical to me personally.