Obviously bands can do what they feel like but being mad at fans for not liking it is just as weird. Though in the case of Opeth their criticism seems to be mostly directed at the extremes of that expression.
same time bands need make some money and I believe Opeth do relatively well by touring. Mikael Ammot and Dark Tranquility IMO is best Swedish metal bands gets most money from tour and music, Sabaton maybe . Amarante do well I sup
Sometimes it just bothers me how fans get entitled. Criticism is ok but you can't dictate how an artist does his art (even if they decide to shit the bag and make duds constantly).
I dont mind Nik Holmes and Gregg McIntosh do ''disco'' music, as they did whit Lost but not under Paradise Lost name. Few Lost songs as singles was OK actually