Lately I've been playing around with different words instead of 'clueless' because the tone changes everything. For a casual, slightly amused jab I like 'oblivious' — it carries that sense of being unaware in a light way. For example, I might write: 'She was completely oblivious to the rumor train circling the office, humming through her day like nothing had happened.' That sentence lets you picture the person and the world moving around them.
For something harsher I reach for 'ignorant' or 'uninformed' when the lack of knowledge feels blameworthy: 'He remained ignorant of the basic rules, which made the whole meeting awkward.' And if I want something softer or more literary, 'at sea' or 'lost' works: 'I felt at sea during the lecture until someone sketched a diagram.' Playing with these alternatives helps me match voice — cheeky, stern, or sympathetic — to the scene, and I usually pick the one that vibes with the character's perspective and the story's mood. I still enjoy hearing which word lands best when I read it out loud.