@Cammy
OK, so you cannot upload screenshots for now at least, but I recall having seen a screenshot or two there at some point. I typically access aminet using ADT, and not so much using web browsers. Maybe what you want is an update of MUIAdt?
As for an amiga app store - the cost of putting it up and maintaining it would never be paid back from the apps sold, and I very much doubt devs would be interested in exclusives, and without a lock-in - what would be the point?