Karaites aren't Jewish.
Why? The split between Karaites and Talmudic Jews took place around 800AD. This when the Masoretic version of Old Testament took its final form (this version is also being used by Protestants)
Karaites aren't Jewish.
Please explain why they are not. Blood lineage?
Their religious beliefs? If it is the latter, their beliefs appear to truly adhere to the the teachings of Moses. The Talmud and Kabbalah are add ons.
Somewhat similar to the Mormons with their add on literature...literature they, like the Talmudists and Kabbalists, esteem on a par with the Bible itself.
Well, so say the Rabbis.... who have to really twist Halacha to get there.