Not surprising that Beastmaster is topping the poll. Even WOTC halfway acknowledges it as such. However, the Revised Ranger and/or Variant Class Features UAs have done a good job of propping it back up.
As for the others, some are certainly the least appealing/interesting subclasses within that specific class, but they still have their niches where they'd shine, and aren't noticeably underpowered overall.
I used to think Four Elements was underpowered, until I read an explanation (I think it was here) of how it aligns near-perfectly to the Spell Point variant system in the DMG. When you view them through the lens of a Spell Point half-caster, with all of the usual Monk abilities, they're actually just fine. It just takes looking at it from a different perspective.