I have a Sharp Roku smart TV. It takes 30 seconds to a minute to load Netflix. I have another older TV with a ROKU device attached. It takes 2 seconds to load Netflix.
The reason being, that Computer technology moves light years faster than TV Technology. Any smart TV you buy today, it's smarts will be obsolete in 2 years. (cpu, memory, wifi........... all get faster).
It is better to have a $100 separate device you can replace.