You make good points and I agree that in this case, hiring a plumber right off the bat would have given you the better outcome.
As you mentioned, there is some risk to doing it yourself and this risk often motivates people to avoid even attempting to fix things. Part if it really is an exercise in learning about the thing and being realistic about how likely you are to succeed.
However, I don't think you should characterize the $300 as a total loss. You probably still have that big screwdriver and set of bolt cutters. Some of the toilet parts you bought might have been appropriate and included in the plumber's repair. You also probably learned a thing or two about plumbing, even if all you learned was that you'd rather hire a professional for future plumbing projects.
I think you're right, and the original post is wrong to say that vans do it better every time, no exception.
However, I think that a van would be a more practical and better vehicle for a vast majority of people who are driving trucks. It's just that people don't care if things are practical, they want things that they think are cool.