Apple had some serious restrictions what you could do with their API:s. There's no reason why Sailfish per se couldn't be adaptable, but Jolla does has some restrictions in their store, which IMO is something that should be addressed with high priority (as should proper support for paid-for apps in store and general support for more APIs). We don't know why, but my guess is that they need to develop better tools to check and QA apps that are to be delivered there. As privacy is one of the important things to the Sailfish-platform, they cannot afford to let through an app that doesn't conform to their idea of privacy (like Apple didn't want anything that didn't fit their platform properly or that was direct competitor to apps/services they provided by themselves). Is Sailfish viable? That remains to be seen. But it needs to attract support from manufacturers, without it there's no way it can live in the long run. Which means, at times it may have to go against the will and priorities of the community.