Yes it's only 1080P but I don't see anything that looks blurry. It's very sharp to me.
Maybe your TV is doing a poor job at upscaling? Because my interface looks fine on a 4K TV.
ZOMG GAIS HAVE YOU NOTICED THAT WHEN YOU SIT 7" FROM YOUR TV YOU CAN SEE PIXELS???? REEEEEE
ALL Android TV graphic user interfaces are 1080p rendered, no matter what device you use.
It's because Google is catering to both - cheap low spec hardware and high powered expensive hardware with the same ATV user interface.
4K User interfaces on low spec hardware is either likely to slow the device down or overheat the hardware and cause further problems.
Some, especially modern premium 4k HDR TV have really good upscaling, so some users do not notice the Blurriness.
Depends how far you sit from the TV as well and your eyesight capabilities.
Compare this to the single spec 4K Hardware devices from Amazon and Apple, which have decent hardware in ALL 4K devices.
Those have 4K rendered User Interfaces and have no such issues.