You are very correct. Almost no one without millions to leverage make a quick killing in the stock market.
On the other hand if you can buy up a million dollars or more in stock that buy alone can push up the price. If not you can just wait until the stock climbs a percentage point or more then sell. That will give you a tidy profit.
I have been invested in the market for over 55 years. The first 5 or 6 years, I speculated, using the age old plan of fools, buy low and sell high. It became apparent that I would never be able to accurately forecast a market bottom or top so I gave up on getting rich in the foreseeable future and adopted a simple plan of dollar cost averaging and have stuck to it for about 50 years. Although it's about as exciting as watching paint dry, it has been successful far beyond my hopes. I have never been completely out of the market or completely in the market. On rare occasions I have sold without reinvesting. Now I am beginning to move everything to cash, bonds, or a trust, over the next few years. It has nothing to do with the current situation of the market just my age and my desire to secure a nest egg for my family.
For some people, the market is a pastime which can be a lot of fun or a fling like a trip to Vegas and that's fine as long as you realize what you're doing is not investing but playing in the market, something I don't do anymore.
Getting back to the subject of this thread, I believe the market is foretelling a significant hit on the economy. It might be short lived or last for several years, but it will comeback. So if I had a money sitting on the sidelines, I would consider putting fixed amounts into the market as it falls; that is I would average down.