Welcome to the forum.
Starbucks is a chain that is normally rejected for “Generic business,” which comes up with the rejection reason you described. It is possible to make a case for a specific Starbucks to be a Wayspot, but it is very difficult to convince of the significance to the community, as you have discovered. Art inside a Starbucks or a mural on the outside of one could be eligible if it isn’t just corporate art: Unique Art
Starbucks often have sponsored locations, which is why you see a lot of them in game. These do not go through the regular Wayfarer process.
Playgrounds meet criteria, as long as they don’t meet location ineligibility. A wayspot only has to meet one of a great place to exercise, explore, or be social, and they normally meet all three. Even playgrounds inside a chain restaurant can meet criteria.
Playgrounds should be submitted all in one piece. Playgrounds on school or single family private residential property should be rejected: Playgrounds
Here is a link you can bookmark explaining criteria.