Abandoning class => job progression would have probably delayed ARR's launch a good while, since you'd have to not only change your expected party structures (plus all systems linked to that), but also have legacy characters make the transition. The shortcut here would be to just wipe all character data and have everyone start on a clean slate, but since 2.0's launch in part relied on legacy players that was not going to happen.
2.0's version of the job was a passable attempt at the song-heavy BRD, but had the main flaw of being tied to resource recovery. Your alternatives would be to design DPS gameplay around songs (Stormblood's BRD was the closest thing we got to this) or to reduce BRD's combat contributions in favor of spamming songs (which won't happen because a} a considerable number of people will not want to play that and b} they'd probably become mandatory for all serious raid groups if the song buffs are strong enough).So that the BRD aspect of the job is simply tacked on top, adding a few extra skills to the kit rather than having the job be crafted around being a bard with its focus entirely on songs and music.
This also means they have the awkward situation where people have to play BRD if they want to play a class that uses bows to shoot people, whilst also trying to make BRD feel like an actual bard.
The bow gameplay issue could have been avoided if the devs had not completely dropped multiple jobs stemming from classes, though that would require them adjusting how job crystals affect the baseline classes and announce upfront that it wouldn't be something that will apply to every class (going against their all-or-nothing approach to design).