I used the OSX App Store for the first time in years a few days ago. For the life of me I could not figure out how to download a simple free app. I had to ask my SO, who usually comes to me for tech questions, how to use it. Keep in mind I've been using computers for decades and have an above average understanding of UI design.
1. Upon clicking the App Store icon and entering my apple ID and password I get a 500 error. No amount of restarting can fix it. After a quick search, one of the top 5 search results led to a cryptic command I had to enter at the Terminal to fix it. This actually happened with a previous MBP and I just never used the app store (pretty much a factory install of OSX on both machines).
2. Clicking the icon to download the app ("GET" I believe) started a loading spinner with no progress indicator. Given it was only a 38MB app, I waited around for a while. Then I took a shower and came back. Still the same loading spinner. Decided to reboot the machine and try again.
3. I searched for the same application clicked GET again and then it turned into a cloud icon. Clicking the cloud icon seemed to do absolutely nothing. At this point I asked my wife who told me I had already downloaded the app to my account and now I need to download it to my machine. EDIT: I just remembered I was seriously confused at this point. I clicked the cloud icon several times and given there was zero feedback I opened both Launchpad and the Applications directory in case it magically already installed.
4. The above explanation made no sense to me. I'm familiar with the concept given I've used every version of Android and I understand I can download previously downloaded things from my account (that I installed on old devices). But that's not how the series of events unfolded. Anyway, I clicked the cloud icon a second (or third?) time and it turned into an install icon and all was good.