Three years into my career and I still don't have a good answer for "where do you see yourself in five years"

Every other interview question I've got a rehearsed, honest answer for at this point. This one still trips me up every single time because the true answer is "I genuinely don't know, and that feels fine to me," which sounds bad said out loud in an interview. Tried the standard version — some vague line about growing into a senior role and mentoring others — and it comes out flat because I don't fully believe it yet. Curious how people who don't have a five-year plan actually answer this without sounding evasive or making something up on the spot.