BNPL should only be used for convenience sake. For people who don't like to carry too much cash around, no need to worry about cash getting lost or stolen or mishandled.
It shouldn't be spending what you don't already have in the bank account. While there is "healthy debt", this refers to business borrowing to generate higher returns rather than buying consumer goods that do not generate returns.
In the context of investing, there is some sense in using margin (borrowing) to invest, as it is possible to generate higher returns than the interest rate. However, be very mindful of the risks involved and only borrow what you are able to return. You cannot fully predict the stock market. If you can, please pm me