Hi all!
Yes, there have been/are many Jewish “sects” both historically (Sadducees, Essenes, etc.) and currently (the so-called “Reform”, “Conservative”, “Reconstructionist”, “Flavor-of-the-Monthist”

, etc. movements). While some/many/most of their members may have been/are Jews, what they believe & practice is surely and simply not Judaism. Traditional, normative Judaism
is orthodox (orthodoxy being a far broader spectrum than many non-Jews, and many non-orthodox Jews, seem to realize; see
jewfaq.org/movement.htm#US for a good summary on orthodoxy & the other, so-called, “movements” within Judaism).
Historically, the Sadducees & Esseners were heretics. (The Pharisees embodied normative Judaism then, much as their direct descendants & heirs, i.e. our more modern orthodox Sages, embody it today.) Currently, the Reform, Conservative & Reconstructionist “movements” are newfangled movements that developed in Europe, in reaction to the Enlightenment. They have junked so many core Jewish beliefs and, in effect, make it up as they go along, influenced by whatever happens to be trendy at the moment & taking care to be “politically correct”. This is Judaism??!! Orthodox Judaism believes that the Torah comes from God; the Reform movement does not. The Conservative movement tries to straddle a middle ground that does not exist. If one does not believe that the Torah is from God, then what’s the point? Judaism is not, and never has been, an everyone-for-him/herself religion. Orthodoxy recognizes that there is a certain set of core beliefs that are immutable & which serve to bind all Jews everywhere, much as they have for thousands of years.
So, while there are/have been many Jewish sects, there is only one authentic Judaism (i.e. orthodoxy).
Howzat?
Be well!
ssv