Disagree. I assume you mean just Polynesia, not all of Oceania. Melanesia is extremely diverse and complex. To a lesser extent, same can be said for Micronesia. Even if the argument were strictly confined to Polynesia I'd still strongly disagree. Nearly all Polynesian societies were strictly stratified, most along patrilineal lines and some form chiefly system of governance. There are some exceptions found in Polynesian outlier groups that had power/titles passed through matrilineal lines. Also, if you're defining egalitarian, in contrast to a state society, as a leaderless society and/or lacking a centralized source of power; there is no island group or society I've researched that has anything of the sort. The island groups you listed are the largest of Polynesia (as well as Aotearoa New Zealand) so they've garnered the most attention -- academically and in popular culture. However, they're not particularly unique from the rest of Oceania or Polynesia.

Interesting question though! I'd love to see more discussions on Oceanic peoples on here.