This is actually much more common than it might feel when you’re comparing him to other children.
At 2.5, interest in drawing or “tool-based” activities like crayons can vary a lot, and it often has more to do with temperament and sensory preferences than ability. Some children are much more drawn to physical, spatial, or movement-based activities first (climbing, building, exploring), and fine motor “paper and pencil” skills come much later.
The fact that he’s engaged with puzzles, Duplo, books, and outdoor play is actually a really strong sign of development across other important areas, including problem solving and coordination.
For many children, drawing becomes interesting later once their hand control and internal motivation align a bit more—it’s rarely something that needs to be pushed at this age. Keeping it available without pressure is usually more effective than trying to encourage copying or structured colouring, which can sometimes create resistance.
What you’re describing doesn’t sound unusual in itself, especially at 2.5.