Plenty of phones with headphone jacks had terrible DACs. If you care about audio quality, external is the way to go. It’s also more sustainable as you can spend $100 once for fantastic quality and keep it forever rather than insisting that each phone have an audiophile quality DAC that will eventually be disposed of.
The one upside is convenience of not having a separate dongle, which is pretty well offset by the significant increase in phone size needed to accommodate the jack.
Given the current phone sizes compared to the phones from before, that all had the headphone jack, the idea that you would need even bigger phones as otherwise it just would not fit is ridiculous.
For the external DAC, you have to balance the "you could buy that once" against all the consumers that are pushed by the omission of the headphone jack to buy throwaway head- and earphones with glued in batteries. There is no chance in hell that the waste produced of both paths is in favour of the jackless phones.
The one upside is convenience of not having a separate dongle, which is pretty well offset by the significant increase in phone size needed to accommodate the jack.