I very rarely take issue with platooning a LHB against LHP. All but the greatest lefty hitters were, at best, mediocre against LHP. Barring a few weird split examples where some lefties don't have extreme splits but you can usually identify those very early on in the minors.
Joe Mauer, Hall of Famer and one of the most pure lefty swings in recent baseball history. Dude had a .740 career OPS against LHP.
Christian Yelich, perhaps the best hitter in baseball for two years and a very good overall hitter for several years more than that, has a career .769 OPS against LHP.
The fact is that the overwhelming number of lefty hitters flat-out suck against LHP. Only the very best hitters are even decent against same-handed pitching.
Long story short, 90% of LHB in baseball should be platoon candidates (ignoring defense and other factors).