In essence, Derech listed 2 mamre chazal stating that childlike behavior is bad for you.
But on the flip side, there is a mahmer chazal that says from my students, I learnt more than from anyone else.
And one of the Rebbes said, multiple things in avoidas hashem can be learnt from observing an infant.
So take your pick.
As far as toys, I’m still hooked on bike riding! (but deeizooger is right, my bikes cost a whole lot more now than they did when I was a kid.)