Seems more like a crutch in that sense, then. If you can’t ride without it, it hasn’t trained you anything.

That's a pretty counter-intuitive statement.

It's like making fun of modern humans for not being able to light their own fire with two sticks, when they lose their lighter wile camping.

Or for someone to not know how to sew a rip in their clothes, when the clothing store is closed. Etc.

Not sure how I’m making fun of anything, training wheels inherent purpose is to train you to ride a bike without them. A lighter isn’t meant to teach you how to spontaneously light fires once it’s out of fuel, nor is dropping off clothes at a clothing store going to teach you how to sew.

You don't need to learn to ride a bike if you prefer motorcycles.

It's more like: you're building a traditional motorbike, some guy comes around and offers you an electric bike's engine, you think "oh well I didn't have the combustion engine yet, so at least I can get to demo/market faster with this and I'll replace it with a real engine when the time comes"...

and by the time you're done with the handlebar, the electric bike engine has been upgraded 4 times and is now better than any combustion engine, so why bother replacing it?

By the time you get to the market, the bike's engine has gone through multiple more updates, is fully self-driving and can fly. It is also self-replicating and now your buyers might not need you anymore...