Creatures in the Monster Manual doShapechange is not havea class featuresfeature.
The only wayspecial trait for monsters that is also a creature to have class featuresfeature is ifSpellcasting since it acquired the features fromis specifically called that in the Player's Handbook, Sword Coast Adventurer's Guide, and/or Xanathar's GuideIntroduction to Everythingthe Monster Manual (ignoring homebrewemphasis mine). All the features that monsters have including Shapechanger and Spellcasting, among others, are not class features even though they emulate them.:
Spellcasting
A monster with the Spellcasting class feature has a spellcaster level and spell slots