On Using Stock User Interface Elements on the Mac
The genius of the Mac is its consistency. Users brand-new to any well-done Mac app are able to understand how to use it pretty quickly, in part because they see familiar buttons, popup menus, sidebars, toolbars, and so on that they see everywhere.
While it’s tempting to put your own stamp on things — as you kind of need to on iOS — on the Mac you can relax and use what Apple has provided.
Not least because Apple has already done a better job than you will. Apple’s controls support various accessibility features, and they behave the way Mac users expect. Both of those things are very easy to get wrong, and when you do it wrong the app feels wrong, and people notice.
Mac users love the Mac because of the user interface, not despite it. Remember this.
Another thing worth considering: it’s cheaper. Writing your own custom UI — and maintaining it across macOS releases — takes resources. The more you use Apple’s controls, unmodified (or minimally modified), the easier time you’ll have when the Mac gets new features and behavior updates.
I’m not saying you should avoid beauty and delight. You want your app to be gorgeous; you want your app to make its users happy. Totally! I’m saying that you should design within the constraints of building a good Mac app. And that working within those constraints makes it more likely, not less, that you’ll reach that goal.