Minion appears to be unable to find add-ons that have moved into the Discontinued & Outdated category. Now at first glance, this makes sense, as there's no point in it installing add-ons that have been classified as Discontinued. But as a result, it also means that you can't uninstall those add-ons either.
Now while those add-ons can still be deleted directly from the AddOns folder, it would be very useful if Minion had a section under its Installed AddOns list where it showed which add-ons you have installed that are considered Discontinued so you can uninstall them. Thanks!