1) can 0.1BTC get you retired in 30 years to this time for real? Wouldn't that put 0.1BTC at a $1 million?
No, not really as a standalone retirement plan. The price of 0.1 BTC is approximately $8k at the current BTC price of $81k. For 0.1 BTC to be worth $1M in 30 years, 1 BTC would need to reach about $10M. That's ~120x from here or ~17% per year, annually over 30 years and would make the whole network worth ~$200T, many times the value of all the gold mined. It’s not impossible on paper but it’s a tough bet for a retirement.
Even if it happens, $1M in 2056 isn’t today’s $1M. If the inflation rate is 3% then it's closer to ~$410k in today's money. A good investment but not a never work again investment in most places.
2) in this world economy now, isn't 0.1BTC something that a 86years old would appreciate as retirement plan than someone in their 30s?
On #2, I'd say that is the other way around. An 86 year old may not have the luxury to wait out a 70% drawdown, as BTC has experienced on more than one occasion and it is still ~35% off of its ATH from last year at ~$126k, but someone in their 30s can do that and continue stacking.
Are people just making a big deal out of this 0.1BTC target?
What about you? Do you think that whatever the value of 0.1BTC is in the next 30 years will suit you enough to feel like yes you are really retired with this amount of Bitcoin.
I believe 0.1 BTC was popular as it was a round number, a number that it is possible to do, and it can get people started. Fine. It gets dubious when videos promise it’s all you’ll ever need because nobody knows what BTC will be worth in 2056. Enough for me? Nope. I would regard it as a seed and continue to add.