SmartThings staff have said multiple times that their typical customer has fewer than 15 devices and uses no custom code of any kind. So the new app should work fine for them.
The problem is that the original business model was that smartthings could be made to work with almost any home automation device and customers would be allowed to upload their own custom code to the smartthings cloud, and that’s what attracted a lot of the power users who frequent this forum and lead to community created innovations like WebCore. And those just don’t work with the new app.
In addition to the new app, there is also an entirely new cloud coming. You’ll still be able to do some custom code, but it won’t work the way it works now. Instead, the developer will have to host the code and then connect with a cloud to cloud integration. The groovy platform will be going away eventually all together. But that’s a topic for a different thread: