Yeah, you could turn a trade into a DCA as well. Lets say that you bought something and you want to sell it as quickly as possible when it goes up, however the price suddenly went low instead of going up, that means that you are not going to end up with anything better, because it would be a loss if you sell. In this situation some people just end up buying more, to make sure that it goes well.
Assume you use DCA for Bitcoin, I agree that DCA is good for your portfolio with a big condition that you DCA with your money, not from any loan or don't use any leverages. DCA only with Spot market and your own money, then a next big step is withdraw your coin and store it in your non custodial wallet.
Don't store it on exchanges because you use exchanges to DCA in. They can freeze your accounts, their exchanges can bankrupt and many risks you can not control. Be your own bank with non custodial wallet.
DCA is not all-in, so why not? But even if its all-in, we still can pay the loan that we take before their due, as long as we are willing to do so. It can be a tactic, same to those business owners outside who also borrow money and use it to widen/expand their business.
If we are only an investor, it is safe to use non-custodial wallets most of the times but traders may need to store a permanent fund inside an exchanger because this is where they can trade continuously. Not all alts are bad, and I already saw a lot of people who does a DCA with them. We must only monitor our assets or portfolio from time to time so that we can act quickly once we see an anomaly on them.