I don't think there is a connection between network fees and accumulation of Bitcoin so network fee shouldn't be a problem that would hold you back from investing on Bitcoin because there is no fee associated during your Bitcoin accumulation, so all you just need is to invest on your weekly target, however I have not heard were any fees would prevent someone from there persistent accumulation of Bitcoin, so possibly you can clarify me on the connection the fees has against your Bitcoin accumulation.
Usually it won't affect but there were times when ordinals paying fees and almost stalled actual Bitcoin for a month and forced them to pay like huge amount let's say 500-1000sat/vb and in that case it definitely affected people from transacting and let's say if someone is investing $50 or $100 every week they would hesitate at that moment or they have to trust the exchange by holding it there which is not recommended since exchange is prone to hacks at anytime.
So that might affected in a way but things back to normalise almost since the Q2 and there's no signs that those kind of spam attack is possible since the hype around ordinals faded away which means it can't be a problem anymore.
Unless he was talking about the withdrawal fees from the exchange which always 5x or even higher than the fee needed depends on the exchanges.
Transaction fee shouldn't be a barrier for you to keep your regular DCA ongoing because if transaction fees are high due to ordinals spam, you can just focus only on buying regularly from an exchange and leave your bitcoin in the exchange for the main time will fees gets back to normal because it will surely come back to normal, you then transfer it to our self custody wallet. During that period that your bitcoin is in the custody of a third party does not mean that you will lose your bitcoin. It is only when you use the exchange as your personal wallet i.e keeping your bitcoin for long in there that you might loose your bitcoin.
Someone who is DCAing cannot prevent keeping his bitcoin in an exchange for some few weeks because if you are using $50 to buy bitcoin weekly and you keep on transferring it to your wallet whenever you make the purchase, in future when transaction fees are high, it will affect you because you have many small UTXO which when you want to withdraw in future might end up eating all your profit and that will become a problem because you are not benefiting from your bitcoin investment that you have pent a lot of time building and hodli for long.
This is why when you are DCAing, you should prepare for high transaction fees in future by piling up your weekly DCA amount in the exchange till it has gotten to $500 and above before you an transfer it into your self custody wallet to save your ass from using your profit to pay for high fees from your UTXO in future.
whoever is using transaction fees as an excuse for not being consistent with his DCA is only trying to create excuses for himself and not looking for solutions to that short termed problem of transaction fee. Like you've said, the majority of us sometimes leaves our funds in exchanges for weeks pending when the fees will be more convininece for us before sending it out to a more secured wallet. It's not like you're unaware that it's unsafe to leave your funds in an exchange it's just the normal process you will get to experience as long as you're doing your DCA.
Buying Bitcoin using the DCA methord doesn't come with zero limitations, thier are obvious limitation and part of it is the issue of buying at the time when transaction fee is the issue or buying when Bitcoin price is quite high. If you're only concerned about these limitations and you're not thinking of the way out of it, you're going to become a procrastinator that will keep waiting for all things to become too convenient for him before he will eventually buy. Waiting for such kind of time is what we all know can sometimes take time and when it's a bit convince for you to buy, the resource might not be available at hand.
Exchanges are not totally bad as long as you're not tempted to leave all your funds in them. In times when transaction fee might become an issue or Bitcoin price might seems too high you can just leave your asset on the exchange for the mean time.