The Calfornia Gold Rush was not in 1949.
"Guaranteed returns" that is "never 100% safe" does not sound like much of a gurantee.
It is easy to get 4-5% on bonds. It would be interesting to see what filters you are using that is precluding finding any.
The title of this blog is about using "only DeFi" for passive retirement income. There is nothing in the article that supports that it is a good idea to use "only DeFi" for this.
Let's change from DeFi to banking to not make it about "crypto" technologies. Telling someone you can retire only investing in Banking (e.g., Wells Fargo, Chase) would be met with cynacism, as placing 100% in any one asset goes against asset allocation strategies.
Not sure what is special about DeFi such that recommending or implying that investing in a single asset is a good idea for retirement.
And none of this speaks to whether 8.6% is sustainable. Blockfi is too new to gauge that, but that will hold as well as someone is willing to pay > 8.6% in interest on a loan. Not just above 8.6%, but enough to cover Blockfi's costs. It will be interesting how their strategies play out if they become a publicly traded company.
I get there is a disclaimer at the bottom of the blog that this is "informational" but not perhaps accurate. I totally agree with that.