OK, so I’ve listened more to the chord structures. Both Ed and Marvin have used the most common pop song structure for the A section (if you’re in C major it’s C/Am/F/G7). As already noted, literally millions of songs do that. In other sections Let’s Get it On does the common variation of C/Em/F/G7. Both songs do that. Again, this is not remarkable. Literally millions of songs do that.
If the argument is that using the substitution of Am with Em is what’s unique, then that’s bollocks. Millions of songs do that.
They both have a slow soul groove. You can’t copyright a slow soul groove.
I have now heard more Ed Sheeran than I ever anticipated I would. As a result I hate Marvin Gaye’s family. But I’ve tried to be fair.
In my view, this case has no merit at all.