Yes and no, unless you have a magic ball its best to DCA. Maybe at best, you could do a modified DCA so that you're not buying Bitcoin when its at all time highs.
If your time horizon is long enough, volatility shouldn't matter. Historically speaking Bitcoin is getting less volatile with every market cycle. I would not be surprised if in the future its volatility is comparable to the S&P500.
Why would any sane person invest in real estate? You have maintenance costs, property taxes, it's not liquid and you can go years with little growth. Not to mention if your area see's hard economic times (i.e. Detroit), the chance of a rebound is slim.
This is not true, saturation points on staking pools exist to encourage people moving to other pools, this causes more decentralization not less. Additionally, from a hardware perspective setting up a pool takes significantly less capital compared to PoW mining.
I'm not sure I get your argument, staking takes significantly less powerful hardware so its very accessible.
Staking pools also have a "saturation point" to encourage decentralization. That way not all 80 Billion dollars worth of ADA goes to one staking pool.
Very hard to see how oligopolies can arise in this scenario when compared to mining operations that are unprofitable to most users (and of course bad for the environment).