It is because Drafts is a cross platform app and so has to comply with the sandboxing limitation for iOS and iPadOS. Keyboard Maestro and Alfred are single platform apps, their remote apps aside, they don’t have to conform to the same cross platform compatibility constraints.
That cross-platform compliance weakness is obviously based on the huge benefit of being equivalent across platforms. Additionally, it is possible to work around in a relatively straightforward and reusable way as I have demonstrated. As such I would not describe the situation as being a steep limitation.
I use Keyboard Maestro, Alfred and Drafts on the Mac. In fact I created the popular “Doctor Drafts” workflow for Drafts and Alfred.
If this was all you have been using Drafts for, then you are probably missing out on large swathes of functionality and use cases. I would recommend you look a bit deeper before discarding Drafts.