People who say 5E isn't complex will never not be funny. I plead for you to play like OSE or Shadowdark and see D&D boiled down to "simple to play and run".
I wouldn't say 5E is less complex than 4E. 3rd ed down, sure.
Complexity is always going to be relevant. It's more complex than flipping a coin. It's less complex than 3.x D&D where the complexity was a barrier of entry for some people. Personally I liked 3.x, but there could be massive differences between a well made PC and one that was just adequate depending on how well you understood the rules.