The question is, how do you own 0.1 BTC in 2022 ?. If you look at the value of bitcoin and market place, it's hard to earn such an amount. The only way to make 0.1 BTC is an investment, but it means you're already rich if you're buying it. Why would you believe it when you already have enough money?. If you go back and invest like $8 to $10, it might become rich. But in today's generation, no one can earn such an amount, not even with mining.
I don't think it is a question of you investing in it once, this is where most people get it wrong. Bitcoin and other cryptocurrencies happen to be what you can buy in bits which is also good, that give the average investor an opportunity to buy little and little to be able to accumulate to that amount of 0.1
BTC and I believe this is doable which is the whole essence of DCA.