The reason for this is that microflows always finish before any show page activity is actually sent to back to the client. A microflow can not be ‘interrupted’ during to ask some user feedback.
If you want to work around this you can split your microflow in 2 parts.
The first part is your actual checks and processing. And when (and if) you need to ask the user for feedback. You can use a show page activity to show a manually created popup screen. Then have the user fill in the values on that popup screen.
You can have a second microflow which you can show on that popup page to continue the rest of your processing with the remainder of your activities.
in the screen below, I would say on click run microflowPart2