I think there's a huge opportunity for GoodTask with the addition of a feature - time blocking. Time blocking has become a huge topic of interest in the past few years. There are YouTube vloggers that focus on this. I've seen a single video on time blocking with a half a million views. They sometimes review software / apps but none of them really are that good. Or they have expensive subscriptions. So most people and most vloggers use Google Calendar.
They use the week view of Google Calendar and simply block out events for their week, each block representing the task they'll focus on during that time, or an actual event they need to attend. The Pros are that it's visually appealing and that your tasks and your events are on one easy to view screen. You can see where you're free time is and how you've allocated your time in one clear screen.
The Cons are that Google Calendar is a horrible for tasks. It doesn't even allow you to block out tasks with Google Tasks. There would be a great hunger for a program that could do a better job.
The opportunity would be to create a screen within GoodTask for time blocking. It wouldn't need to be tied to a specific list. You just need one screen because we just have one set of hours to work with in a week. The screen could look just like the week view in Google Calendar. It would include your Google Calendar events which could be resized to make them longer or shorter or to be dragged to a different day/time within the week. And, in that view you could add your tasks, drag them to a time/day and resize their duration just like events in Google Calendar. The advantage over Google Calendar is that you'd have tasks along side events and have the full power of GoodTasks for your tasks.
I guarantee you, if you added this feature and sent review copies of GoodTask to the many vloggers that create videos on Time Blocking that you'd get a lot of interest in GoodTasks. Like I said, there aren't really any good solutions and people use Google Calendar because it's the best there is right now. But using events as tasks really sucks.