That is the best method of buying bitcoin DCA, that will minimise your risk. People that think bitcoin is for the rich i can says they don't really know anything about crypto that is why they said so. Because someone that is educated about crypto will always know that you can buy bitcoin in any amounts from 1$ upwards.
Don't say Bitcoin and crypto together or Bitcoin and altcoins together. Your post is like knowing Bitcoin is also knowing altcoins or knowing altcoins means understanding Bitcoin.
DCA is a good investment strategy especially with Bitcoin investment and accumulation while it can work bad if you apply it with altcoins or shitcoins.
With Bitcoin, if you DCA and hold bitcoins a long time, you get good profit but with altcoins, if you hold them a long time, you get big loss. If you DCA altcoins a long time, you lose bigger capital.