I don't think the Cardinals have lost or their touch on drafting and signing pitchers who can be good or better as much as they have had to tap into that resource pool to seek trade help -- sometimes on trades that more or less backfired.
Zac Gallen was drafted during the Flores scouting director era.
Him, along with pre-Flores picks like Sandy Alcantara, Zac Gallen, Austin Gomber would all look like pretty big helpers right about now, if available.
Dakota Hudson too, if healthy.
Some of those trades (Gomber for Arenado, for example) made sense and worked well.
Others, like Alcantara in the Ozuna deal, made sense but have not panned out so well. He's an opening-day ace. Ozuna had two average at best seasons with the Cardinals before departing.
The Cardinals had to tilt their focus toward getting and developing some hitters who could help in the future, because there was too long of a track record of them not emerging.
The pitching has not fallen off a cliff as much as it's been traded away.