The Android one I can: Check tasks I've done, scroll the list of tasks, select individual tasks, change the view (which opens a selection dialog), open the configured view in Todoist, and add a new task to the configured view (which opens a small UI over my home screen).
The iOS one allows you to long press to change some settings, select individual tasks (which opens Todoist completely), open the configured view in Todoist, and add a new task to the configured view (which opens Todoist completely). It also has __very__ limited options for where you can put it on top of the already-limited sizing options. I can either put it at the very top of the screen, the middle of the screen (2 rows of apps above, 2 rows below), of the very bottom of the screen. While the Android one can be resized to basically whatever and put anywhere. You can also only see 3 total tasks in the widget since you can't change the size, the text size, and you can't scroll. I might as well just click the app because it offers __very__ little that just tapping the app doesn't, or notifications don't.
No wonder not many widgets are being adopted for iOS. They're extremely limited. And that's all on top of the point another comment was making about people making websites into apps with React Native or a wrapper which makes it really hard to create widgets, especially with things like heavy memory/CPU time limitations placed on widgets in iOS making it hard to be able to boot up the app and get enough data to create a widget with inside those limitations. Let alone making the iOS-specific APIs and whatnot available to your app.
I think taps are supported, I don't even know if you can scroll in a widget?
The reason for this is supposedly battery life. For the bigger widgets on an iPhone that feels a little over the top, but the widgets system underpins the lock screen widgets which are now possibly always on, and the watchOS "complications"/widgets, which can also be always on. Because of that I can understand it.