Getting lost because you forgot to wind up the stopwatch won't cut it either.
The only thing which might "cut it" is if Stansted moved by 10 miles, in the middle of the night, and they didn't tell anybody
I would still draw lines on the chart and follow a paper plog.
I don't think MM is any good for flight planning. It is a very nice moving map app which shows at a glance where you are, and shows the airspace quite well.
One can do crude planning with it, by drawing tracks, but it is a real hack. I fly VFR using an ex-Navbox plog, and run the MM moving map just as belt and braces, or if doing an un-planned bimble.