The way you designed your application is ok... but only if your service will come to handle other things than just wrap up the repository methods!
Always keep in mind the YAGNI principle that says:
Always implement things when you actually need them, never when you just foresee that you need them
Let's say that you have a user story that says that whenever a product description is not found in your DB, you should retreive it from somewhere else (calling an external service or something). Then it seems obvious that your ProductService will have to have a
private readonly IProductRepository _productRepository;
but also a
private readonly IProductDescriptionService _productDescriptionService;
In that situation it really makes sense to add a service layer on top of your repositories.