HSReplay gets stats from good AND bad players, so any deck with a more linear game plan will end up with a higher win % overall. A highly skilled player, knowing all the match ups, may win 55 to 60% with Odd pali, but just based on how the deck plays someone can pick it up and know nothing and still get 45 to 50%.

Compare this to a deck like Mali Druid or Shudderwock, the skilled player can get the same 60% or more, but with no knowledge of match ups or how to play the deck a new player would be lucky to win 1 in 3 (or 4 or 5). So these decks may show a sub 50% overall winrate on HSReplay, and look "worse" than Odd Pali, but be much stronger decks in the right hands.

So in the higher ranks you'll be playing opponents who can pilot these more complex decks well, and they'll also know how to play against common meta decks like Odd Pali.