One point here I definitely agree with is the "fun time" bit.
I find fun helps me be more productive. I use a system for my productivity where I for example, exercise every day or study every day that I work / study from home or clean the fish tank every second Tuesday but I also have fun scheduled into that system as my productivity is worse when I don't allow this. This last couple of days I have started my day off with a frog sandwich. This was based on seeing the saying "eat your frog first" meaning you do your worst, hardest task of the day first but also knowing that it is sometimes recommended to do the most fun and best task first because it gets you thinking in a positive, productive way that helps later. So I made a sandwich. THe last couple of days I have played a match of Overwatch first thing (I have it in my system to play video games every day that I study or work from home but I always choose something with matches etc instead of something open ended like WOW so it doesn't get overdone and reduce my productivity rather than increase it which is what it currently does), then done my hardest task for the day IMMEDIATELY afterwards so I can tackle my hardest task(normally something to do with study) while I am benefitting from the positive feelings, lack of stress and dopamine hit that came from doing something fun like playing the video game, and then I do something that is not my hardest task but is productive (like editing a lets play). Then the rest of the day is based on doing whatever else is in my system and in the app I use, EpicWin but I always do the minimum that is in my system. So far, both days I have exercised as my next activity straight after video editing. I improved my time management adn productivity when I went from using goals only to having a system, then I improved it again with using EpicWin (which also helped with remembering things as things can be put in to repeat each fortnight etc - like paying rent!) and this frog sandwich seems to be an improvement again. I'm getting more done by midday with this approach and I'm feeling more accomplished and more relaxed and less stressed. Starting with fun, then immediately getting the worst task out of the way really seems to help. I think fun time really cannot be stressed enough. It is important. And obviously some companies think it is important too or places like Google wouldn't have fun things for employees. My productivity has improved by planning when to do my non-productive things, my fun things. I agree with a lot of the points you have made, but the "fun time" one is one that I think is the most important.