You might be interested to check out
https://medalla.launchpad.ethereum.org - this is a public testnet of Ethereum proof of stake
https://beaconcha.in/ - this is an explorer for the proof of stake testnet. The proof of stake chain is called the "beacon chain". If you want to believe in PoS when you see it actually working, this site is actually that! The public testnet launched in the last month or so. They are hoping to launch mainnet later this year.
It's another useful explorer.
There's also https://eth2stats.io/medalla-testnet
It's not an explorer, but a way to keep tabs on your (and others') nodes when it's not handy to e.g. connect with ssh. Only a small number of node operators are currently reporting to eth2stats, but hopefully that number will grow over time.
Compared to stonks, crypto exchanges have APIs that you can use to access them directly without a broker and lower and simpler fees (i.e. no minimum fees per trade, so you can easily make a bot and test it with low amounts and whatnot). Some jurisdictions don't tax crypto trading profits or have a lower rate.
RE 1. I keep hearing this for years now; I'll believe in PoS when I see it actually working.
RE 2., I just tend to keep finding (or being approached with) really bad ones. Last time I got excited was with FileCoin, but that seems to be... not moving too fast at all. I'll look into the quadratic funding/voting thing; it looks interesting, but from the brief overview, it's not necessarily crypto-specific.
RE 3. That belief is what I consider naive - or just perhaps I strongly hope it's wrong, because of point 1.
RE 4. That's true. I just keep hitting the obviously scammy ones - but that's perhaps because I'm an outside observer. Honest people who are knee-deep in crypto are definitely able to separate the wheat from the chaff.
RE 5. I don't doubt your friends are thoughtful and have strong moral compasses. But in that last statement, I was talking about trading these currencies in general - which counts in scam coins, bullshit "crypto! AI!" startups, and various criminals using cryptocurrencies for illicit trade. I would think this point is self-evident - an unregulated space with features that give more utility to criminals than to law-abiding citizens will, by definition, attract disproportionately more of the former than the latter. Also, when I say "disproportionately more" I really mean it, it's not a code for "everyone is bad".