This doesn't really match my experience for my own career or as a manager. Plenty of great engineers don't have a plan beyond "learn and get better," including those that have traditionally-successful careers (e.g. director+ at top tech company).
I'd expect that to matter more if you're, say, trying to be a founder - I can see that benefitting from intentional planning. But for careers at big companies, "learn and get better" seems good enough (and if that qualifies as a plan, I don't think I've worked with anyone that doesn't have a plan).
There’s also a difference between not having a plan and not being able to articulate your plan. Articulation is a skill that needs training and people who rarely need it are rarely good at it. I can take people who have strong plans and train them to articulate it in a few weekend sessions but someone who doesn’t have a plan requires multiple years of work to develop a plan.
"Learn and get better" is absolutely a plan and a great basis to build on, though it's nice to know if there's something in particular they'd like to learn. I've never encountered a candidate who will say they want to learn but not have an idea of what they want to learn...just candidates who have an idea what they want to learn but are afraid of saying the wrong thing in the interview.
I'd expect that to matter more if you're, say, trying to be a founder - I can see that benefitting from intentional planning. But for careers at big companies, "learn and get better" seems good enough (and if that qualifies as a plan, I don't think I've worked with anyone that doesn't have a plan).