The notion that we shouldn't or can't talk about early "Judaism" because there was no normative expression borders on bogus. Also bogus is the notion that there was "normative Judaism" (=Pharisees) alongside other sectarian Jews like Sadducces, Zealots, Essenes, and the rest. Normative means that one understands one's particular expression of Judaism as normative. The Pharisees, Sadducces, Essenes, Zealots, etc. were Jewish - they all participated in Judaism as individual expressions of it.
To talk about early "Judaism" does not have to imply a static monolithic entity. It can just as easily refer to a dynamic religion in the second temple period with multiple expressions. It means that all Jews in this period identified with and participated in a particular set of traditions, practices, narratives, and memories as a community, although their interpretation of these may have differed from each other.
As I spoke in my NT class today, all expressions of early Judaism shared in a particular covenant relationship with a particular god YHWH, felt that the Torah was sacred and central to that relationship, and had a shared set of presuppositions about how the sacred texts were to be interpreted. They all worshiped YHWH as a god of holiness, a worship that was centered around the Temple and synagogues and that followed a liturgical festival cycle. They all shared a cosmology that pictured an enthroned king-like deity surrounded and supported by his court of angelic host. They all were involved in apocalyptic-thinking about Israel's future (even if to combat it as might be the case with the Sadducces).
So I retain the word "Judaism" in my academic vocabulary, and have begun resisting using the plural "-isms" except in rare well-defined cases.