If you want to improve a REST API beyond GET/POST&PUT and DELETE the next step would be adding the push functionality to send new data into your web applications. With ASP.NET Core and SignalR you can add this functionality with ease and keep your application up to date without letting the clients reloading their page manually.
Always think that Signal IR is something hard to learn and use but with your quick tutorial it is really easy to implement and use. Good job and look forward to some other new .NET tutorials.