Sure its a catalog of your local media served via an API, with metadata enrichment, built in transcoding (hardware support too) and multiple user support (watch history, recommendations etc).

Its not just a web app, I would say most dont use the web app directly, instead they provide clients (Android/iOS/Roku/AndroidTV/WebOS/Tizen) that are in official app stores. This is the big thing for me, being able to just install the client on your TV and not worry about it is great.

Often the clients are just wrappers of the web client with native integrations, but they work well.

Plus there are loads of 3rd party plugins to extend it, and alternate clients, Im a fan of https://github.com/jeffvli/feishin for music duties personally.