Concur. As the old saying goes, I don't care about left-handed pitchers, I care about getting left-handed batters out.
Looking at OPS-against by our top 6 by games started, Lopez/Gray/Ryan/Ober/Maeda/Varland....
Lopez and Gray really stifled right-handed batters. Gray didn't have much of a platoon disadvantage, while Lopez's was pretty significant in the normal direction.
Weirdly, all four of the others had a reverse-platoon split in 2023. Ryan and Ober were sort of league average against right-handed batters, Maeda* and Varland were pretty terrible against righties. But against lefties all managed to hold the opponents under .700 OPS, much better than MLB average.
Surely not a repeatable outcome, unless pitching coach Maki has some kind of voodoo no one else knows about.
Still, unless and until something changes, finding a lefty starter is pretty low among the priorities, as opposed to just locating a top arm, period.
* Maeda's season was split between trying to tough it out before finally going on the IL, and then being pretty effective when he came back, so I am a bit skeptical about slicing and dicing his data without taking that into account.