The reason why video playback is not available on 3.0.0 and onward is because Nintendo removed the mp4 playback feature of the browser applet.
They did so on purpose, because they fear that the mp4 player could lead to another exploit like it did on the Wii U for 5.5.1.
That's the reason why they removed video playback starting on 3.0.0. It was available on 2.3.0 and previous versions.
And I also believe that the reason the Switch doesn't have a proper browser app is due to the same reason, a webkit exploit.
Stupid Nintendo, no matter how hard you fight back, you will get your asses exploited anyway.