Could one obtain a worthy skill at a trade school and become successful? Most certainly. A person with a construction trade such as plumbing, electrical, or basic carpentry could do very well. Doesn't even have to be in a new construction setting--re-modeling of existing homes is booming in many areas.
Many would argue that a 2-year college degree is enough; in certain fields perhaps, but those degrees are limiting, because they often focus on a specific technology or focus in a field. This might include a particular programming language, or a specialty like dental hygiene. These degrees might get you into the door of a company with a very targeted need, but a four-year degree is seen as more versatile, providing much more foundational skills.
One could argue against all of this, saying that there are plenty of self-taught, college drop-outs who've become successful in their businesses. Yes, that's true. It's a much more difficult road though, and not everyone has the ability or entreprenurial skills to start and run their own successful business. Not everyone can be a "people person" and be effective in sales. Not everyone can "get in with a good government job" by knowing someone in the union, and retire in twenty years. Right now, having four-year degree from a reasonably decent college, with a meaningful field of study is a good back-up plan.
I think that's the key. My son who is studying biology wanted to be an actor and study theater in college and we talked him out of it. I know a lot of parents hold the view that you should encourage your child to "follow his dreams," but we took the view that if your dreams don't have a very good chance of becoming reality, don't waste your money on getting a degree in that field. He's very excited with biology and chemistry and everything he's learning now, so it seems like it all worked out.
You made many excellent points!