Yeah but sometimes DCA won't work if fees are way too high just like what had happened few weeks ago during and after halving. But yeah no doubt DCA would be the best way to accumulate little by little until we are happy enough with our desired amount of investments.
In my opinion, there is no harm in storing BTC temporarily in an exchange wallet, as long as transaction fees are still high and waiting a few months is not a burden for a holder. Exchange wallets are also not as bad as you might think, as long as you don't store BTC there for a very long time. Just wait for normal transaction fees to return, then you can immediately purchase BTC to store in your personal wallet.
In fact, high fees will only prevent us from selling BTC, and that is in accordance with what we are doing, namely holding for longer. As long as there is still a positive trend regarding BTC price movements, high transaction fees will only have a significant effect on people who frequently use it for transactions.