Your mistake was not buying the top but rather buying an altcoin.
Buying the top (of Bitcoin) and not selling, in the past has always been profitable, no matter how high the price was that you bought in. I cannot say the same about any altcoin or token. They are more of a dangerous investment which have been known to go to 0.
Don't put your faith so much into signals either. Trading is as random a lot of the time as gambling.
Yeah, if you bought at 19k during 2017, then you could have sold at 60k+ during 2021, or if you bought at 60k+ during 2021, you could have sold now and still be in profit. Buying bitcoin is great at any price, and you can make that profit, and if you end up with something else, like lets say you bought at one level, at the top, but you DCA and make that profit some other time, then you are going to end up with better return.
It should be very important for that and we can make some profit with it. I understand it is not that weird and we should be looking at this in a different approach. That is the most important difference and we can make some profit from DCA and being able to make some profit from it as well. That's the key figure here and we can make it happen.