The article title seems to oversimplify things a little with the "too hard" bit. I read a couple dozen negative reviews, and most cite poor performance, copy-paste boss design, too much hp and/or too little player damage, and unfair mechanics. Sure, those last two aspects could be seen as "too hard", but they read like there's a difficulty spike from the base game. Whether this is a case of players needing to adapt or whether there's an actual issue here, I don't know, but seems there's more to this than just a case of players complaining about a hard game being hard.