A REST API can also give only the fields you need if coded accordingly. My REST APIs will accept this https://apibaas.io/endpoint for a response with all the fields, this https://apibaas.io/endpoint?fields=a,b,c,d for a response with only the specified fields, or https://apibaas.io/endpoint?except_fields=e.
A REST API can also aggregate results from several entities if you want, you just need to code accordingly.
Developers just need to have an open mindset and not blindly follow the herd. Also, follow API design first approach and use the tools at your disposal to design the API with OpenAPI specs. After you are happy with your API design give it to your consumers and address their feedback in the specification before you start to code the implementation, and repeat this as many times as needed until the API specification is beneficial for both the developers implementing it and the ones consuming it. During this API design first process you will discover many issues with your initial idea to solve the business requirements, thus saving you from discovering them after having already some thousands lines of code written.
