A "Beginning" class often assumes you've done some dancing, and they move at a reasonably fast pace. I was always a slower learner than many others, partially because I had only (publicly) danced 3 or 4 times in my life before age 40. Many instructors label their class “fast beginner” or “beginner/intermediate” so they can get away with teaching whatever they want, based on who shows up.
The problem for the instructor is simple: If they really teach what a beginner should learn for long-term success, most people get bored and won't return. As soon as someone learns "basic," most guys want to learn complex turn patterns and the ladies want some sexy styling. So instructors move it along, knowing most people aren't doing basic "well," but they're doing it "good enough" to move on to more steps.
Since most people are dancing for fun and social reasons, that's fine; but if you're serious about improving, you probably need to look toward private lessons to supplement your group classes. (More on selecting instructors in a future article.)
At the ballet you see girls dancing on their tiptoes. Why don't they just get taller girls?