Very thorough and well thought out response. I wouldn't buy Bitcoin primarily to stave off inflation, although that is a benefit. I think we can all agree that inflation is here. Therefore, being diversified in finite stores of value makes sense (metals, real estate, collectibles, land, bitcoin).
Bitcoin's (crypto's) price has historically been volatile and this is the cost of admission. People bought Bitcoin in 2017 for 20K and they may have regretted it but if they held, they feel better now. Personally, I have adopted a DCA approach.
I agree that trying to forecast exact prices is speculation. However, there is still a much larger pool of potential buyers for Bitcoin than for almost every altcoin. This is why there is discussion about a Bitcoin ETF and not a BNB or ADA ETF.
1) Environmental impact is mainly FUD in my opinion. More energy is used in the mining/transport of gold. People don't even realize the resources for mining Lithium or whether their Tesla batteries will ever breakdown.
2) Low bandwidth is why the narrative changed from digital currency to store of value. You don't see people buying cups of coffee with gold. Yet gold is still viewed as a store of value commanding a 10 trillion dollar market cap.
3) Tech is locked- There's a lot of effort making the tech more effective. We have Square and many other Bitcoin rich billionaires who want to see it succeed. With their resources they can bring their visions to reality.
I like diversifying with Altcoins, but in reality, they won't yield more stable returns because they all compete with one another. Look at the platforms: ETH, ADA, DOT, BNB, LUNA, EGLD, SOL, MATIC, ZIL, and others. I don't interact with Defi on ETH because the transaction fees are insane- I can do similar things on BSC or Polygon for a fraction of the cost and at a faster speed. On the other hand, BTC is in a class by itself and therefore provides more portfolio protection.
With all this being said, crypto is risky and speculative. However, not owning any Bitcoin or crypto is also risky and speculative. No financial advice here. I think we both can agree that diversification is key. My argument would be to hold more Bitcoin for the long term than alts.