My 15mo hasn't the foggiest how to get a shape in the correct hole, not even when the manufacturers have obligingly colour-coded the holes and put a little picture clue on each. We're talking choice of 5.
He doesn't seem interested in systematising things according to category either. We don't push him in any way, but I leave simple wooden puzzles by his bed (shape sorters, ark, dress-up bears, wooden blocks that make a picture). He loves playing with them every morning, but for him this means disassembling them and posting all the pieces under the bed one by one, or trying to work out what they're about and eventually dashing the pieces against one another in frustration.
I think he's just been focusing on other things, like running, climbing etc. and he's got good fine motor skills and is very emotionally sensitive and aware. (He's a high needs baby). His favourite toys tend to have wheels or announce, "Ground control to Spaceship One", "Hello Puppy", etc.
Will it all come together, people?