I don't think that investing in stocks is inherently a casino; if I buy a share of AAPL then there's not inherently a loser; if the price goes up then both Apple and I benefit from this. Even if it goes down, I still retain whatever value the stock is currently worth. Still, I used to make sweeping statements about finance that I don't agree with anymore; I used to say short selling was inherently evil for example, and I actually don't think that anymore [1].

I do think that option contracts might be evil and a glorified casino though. It feels like they kind of end up with a means of really really rich people to extract money out of poorer people without those people actually gaining anything back; since options are (as far as I'm aware) a binary "make money or lose your entire investment" situation, and each transaction requires a winner and a loser, it definitely is very analogous to a casino.

I do call myself an "investor", but 95% of all the money I have in the market is in low-risk ETFs (VOO and VTI), which I don't think is gambling.

[1] Well, they might still be evil but I think it's a necessary evil in order to put downward pressure on the market to avoid ponzinomics.