A few of the filters are somewhat useful, but they really need a slider to control the intensity of the effect.
The sharpness filter is pretty useful to compensate for blurry videos such as when watching 1080p on a 4k screen, it's just a tad too aggressive, and would be even better if filters could be tied to specific resolutions.

Seems like it's asking for more permissions than the extension should need, there's really no reason for it to get permission for anything not on youtube.com