This bothers me too. On mac, I would get distracted just as easily, and I agree with others here that internet-capable devices are just distracting in general and any on-device tricks or features like Screen Time can only do a little bit to keep you from getting distracted. Instead, you can look into task management or practice focus through meditation.
One main difference with macos, though, is that ipadOS lacks a desktop and Spaces. On mac, if I got distracted, at least the windows I was working on before were all still open in the same place, waiting for my return. On ipad, instead, there is only the App Switcher, a big pile of all the apps I've ever opened, with no way to keep me locked in. I would also love to know more fixes for this problem.
One fix I've found is to make a Shortcut for workstations I use a lot. For example, I have a language class Shortcut which opens two apps in Split View (the relevant note in Goodnotes along with a dictionary app) and another app in Slide Over, and activates the work Focus Mode. Saves time, and I find this way of opening apps already decreases my chances of getting distracted. But it doesn't work with Stage Manager (which lacks most Shortcuts integration), and can't be used for tasks where the apps I use are not the same every single time.
