As long as we're talking about what's good with Zwift, I'll add a few things that I've always found bad about it. I'll give your questions a try
I really hate the way Zwift displays elevation profiles. If I'm riding a pre-selected route, I don't understand why Zwift won't give the option to see an elevation profile for the entire route, with distance markers on it and gradient colors. The current elevation profile that is displayed (on a tiny sliver at the bottom of the equally useless "mini map") seems completely arbitrary. There are some climbs (like the Bonus Climb in Watopia) that are super steep, but barely register as a climb on the elevation profile. A total route elevation profile with KOM's and sprint points doesn't seem that difficult to figure out. You can get this info concurrently running Zwift Power live where it provides the entire elevation profile .
Also why are there no customization options for other metrics that are displayed? Average speed and power seem like pretty basic numbers that people have interest in, yet Zwift doesn't provide those until the ride is complete. Same thing Zwift power live in the background gives you avg speed, watts, distance traveled, distance to go, normalized power, current HR, etc. Not only your stats but for everyone else's in the event.
Why do they continue to include a confusing "trainer difficulty" setting, which incorrectly implies that a lower setting makes the game "easier" when in reality it just makes the grade changes less realistic. I feel like they should change the name of the setting and provide more of a description on what it does. You don't seem confused anymore, you described it. The real problem isn't the name. It is the concept that the same watts are required whichever setting you have it on that causes confusion. If you have a better name to explain this I would love to hear it.
Why do I still, in the year 2022, have to first start a ride then pause and page through a menu to see my overall progress on a challenge? I can see my total miles/elevation in my basic profile from the website, but I have to be in the game (and on an active ride) to see my progress in a challenge. This makes zero sense.
Similarly - why doesn't Zwift provide other profile stats/metrics like % of routes/roads ridden, a heat-map feature that shows all the routes you've ridden, and which ones you haven't? All-time PR's. Averages for power/intensity/mileage based on days or weeks. Why do I have to piggyback Strava on top of Zwift to track all of this when Zwift already has all the data? Most of this is provided in the Zwift badges page or your Zwift Power profile page.
OK - rant done.