I used to rely on the getSingleItem method from the Shopping/Finding API, but today it seems to be deprecated. The new Browser API doesn't provide the same level of functionality and is not backward compatible.
Currently, there is no single API that works seamlessly for both simple and variable items.
For simple products, we have getItem, and for variable (grouped) products, we have getItemByLegacyId, but there is no programmatic way to determine which one to call. Moreover, the item_group returned by the new API doesn't provide the same level of detail as the old API — for example, it doesn't return all the possible sizes, colors, and other useful information. The data returned seems to be incomplete and not as detailed as before.
Our production apps are no longer functioning because of these changes. We really need the Trading API and the Shopping API back, as the current APIs don't make sense for our use case.
