is my assessment mostly accurate?
No, it is not.
Prop trading -- understood as extracting money out of financial markets -- is very diverse. Some people care about milliseconds and build their own microwave links between New York (actually, New Jersey :-D) and Chicago. They make millions of trades per day and make a tiny fraction of a cent on each trade. Some people care about long-term value, trade a few times a year and hold their positions for years. Some people do arbitrage. Some people do distressed investing. Some people do convertibles, or M&A, or IPOs. Some people make macro bets. Some people do something else in the markets. All of them are "real professionals".
The type of prop firms you are describing are really just back office pools or trading arcades. Say I am a broker-dealer and I have a business that attracts chumps to deposit money with me, and I will allow them to trade through me, and all the traders can share expenses like office space and other services. The burn out rate is really high. Notice that this supposed "prop firm" is making most of its money on commissions from their own traders! and not actually realizing gains from their trading employees. Contrast this to a division in an in...
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