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It seems to me that all investments involve risk. What makes borrowing to invest in BTC any more risky than investing in a start-up, opening a business or buying a house (which may be full of defects, for example)? If the person's financial situation is stable and the banker, after studying the file in depth, is OK, I don't see why you can't borrow money to buy BTC. In fact, this is what some large companies do.
Well, you are somehow correct with the points you have raised.
However, loaning money primarily for investment is definitely a risky move given that you double the risk on your side. Not only do you have to pay your loan when it matures but you are also relying on the fact that your investment must have profited by the time your loan is already due and demandable.
What you mentioned back in 2017 was completely valid given the risks involved. But this falls into the category of "high risk, high reward" where a person can either experience both extremes (win or a loss).
In conclusion, I still advise persons to NOT loan money primarily to invest into another investment especially if they do not have a source of income that can cover such debt. The reason is simple- why loan when you can purchase it with your savings?