The text looks difficult to read in that pic but in reality it is much clearer, more so due to parallax as well.
No it doesn't really look much better in reality.
In fact, the Topic Starter is right in the sense that for details like this, they undermine their own design philosophy to keep things clear, by desperately holding to their other "flat design" philosophy introduced in iOS 7.
Every UI designer knows that in order to make white text readable on a white/light background, you have to add a (very subtile) drop shadow below the text (if you don't want to mess with text borders). In case of the lock screen, they don't add this anymore (unlike in the past) because they want to keep everything flat. In an attempt to solve this, they added some tricks:
- When you select the lockscreen wallpaper it detects if it's light or dark, and automatically change the lockscreen text color to white or black. In the examlpe of the iPad wallpaper with sea and rocks (that came with iOS 11), you can see this light/dark detection fails and it renders the text white causing it to be unreadable. A very subtile dropshadow would have fixed this.
- Depending upon the the wallpaper overall lightness, iOS also decides to choose between dark or white font of the text below the launch icons on the home screen. This mechanism also fails in a lot of cases. In case of an in-between wallpaper/photo (containing very light parts but also darker), it simply darkens the whole photo when chosen as wallpaper, and keeps the textlabels white. In past iOS the readability of the launch icon text labels was clearly better, due to a subtile dropshadow on the text.
- [EDIT:] The time/date on the lockscreen however, actually DO have a (very subtile) dropshadow in iOS 12. This is visible when you add a background with a light/white top but dark bottom so the font-color is still white. But still strange that they don't seem to apply this on the text at the bottom, which is the subject of the design flaw in this topic...
Luckily Apple nowadays re-introduces subtile drop shadows on some places, to create some depth/UI clarity in iOS. But as long as the flat design continues to be the trending fashion for some more years, it won't go back to iOS 6 style design that had UI drop shadows all over the place.
Personally, I hope that in some years, they will evolve more and go in-between with the UI design. Some aspects of iOS 6 were nice, but a lot of aspects from modern iOS are great too. It actually improved greatly since the first flat (and buggy) UI attempt with iOS 7. Modern UI things like the realtime blur effects are great, while some old things like the glass/gloss effect on icons look hugely outdated now. Also adding a dark-mode to iOS will hugely improve eye strain for a lot of people, caused by the light UI design.