Why not then hourly? If daily is more beneficial than weekly, then certainly hourly would be more beneficial than daily. What about investing every minute, or second?
If you can set up hourly trades, then why not? The likelihood is you are going to get stung for fees by making more frequent smaller trades than by making one larger trade every week. Once you get to hourly trades, you are looking at ~720 trades a month, so unless you are investing huge amounts, you are also going to start getting hit by rounding errors in both the traded amount and the fees paid (neither of which will be in your favor) from your multiple very small trades.
I think it is more important to get the best return for the least amount of effort.
The least amount of effort is to just set up automatic recurring buys once you've worked out which structure gives you the best overall fee rates.
The market has gone down and so his profits have gone down. That's not an argument against DCA. Yes, if he had perfectly timed the market then he would have made much more, but conversely, if he had poorly timed the market then he would have lost a lot. The whole point of DCA is to minimize risk, not maximize gains.