the equation of a skateboard with a toy seems to be made just because they are both inanimate objects used for play. that's as far as the comparison goes. but in fact toys are trifling things that anyone with no prior experience can pick up and amuse themselves for half an hour or whatever and be done with it. a skateboard is an instrument that you are constantly perfecting in terms of the way you use it, how you think about it, etc. in my opinion, that makes them incomparable.
By that definition, there are many toys that couldn’t be called toys then. Bikes are considered toys, as are unicycles, balance boards, diabolos/yo-yos, fingerboards, jump ropes, kites, marbles, frisbees, air hockey, foosball, and many others I’m forgetting. They all require skill, and you can “amuse [yourself] for half an hour” with any of these, as you can skateboards, with no prior experience, but to be
good at any of them requires practice and the development of skills.
In fact, I would argue that the majority of people who have ridden a skateboard have probably picked it up and amused themselves for a short time and then never touched it again. The majority of people I know have at least tried to skateboard, but didn’t take it up. That is even more support for it being a toy.
Just because something is a toy doesn’t make it bad or mean it’s worthless. It’s worth a great deal to the right people. But it’s still a toy. If that bothers you, then the problem may lie with you. I’m perfectly happy being a 31 year old man who plays with toys.