You are absolutely right that it is possible to make excellent movies for cheap. Statistically though, you are wrong.
Believe me, there are many *very* ingenious people out there trying to make good movies for as cheap as they can. The fact that they don't succeed as well as big studio movies is not because studios shut them down. Of course from time to time sometimes it is because the studios don't have the proper vision. But on average, statistically, it is because the movies that are independently produced generally aren't good, and once you've made a couple of narrative movies you will understand money has often a lot to do with it. It won't buy talent, but talent without the means won't work.
I'm not even talking big VFX stuff. People want entertainment that doesn't make them wince because sound is bad. Or a picture that is hard to get into because you keep being distracted by lighting discontinuities.
As to the "classics" that you emphasize, which supposedly cost less money back then, you are so wrong. In spite of all the hardships I mentioned, it is still a heck of a lot cheaper today to make an independent movie than it was back then.
Put those budgets in today's dollars: Casablanca, $15.2m in 1942 dollars = at least $162m of today's dollar according to http://www.measuringworth.com/. Citizen Kane (a 1941 release) would cost more than $100m in today's dollars.
"The Wizard of Oz" cost more than $500 million in today's dollars. That is more than 3x as much as "Transformers" which you apparently despise but which a lot of people--and not just children--have actually enjoyed paying a ticket for (I am not one of them).
The amount of work put in those masterpieces required huge amounts of resources, because technology wasn't as good as it is now. Without studios willing to bet such huge amounts at the time you would most certainly not get to have enjoyed any of the classics.
Go make a movie, face an audience with it, and then we'll talk. Till then, show some respect to the people who work their asses off, and pay for your content.