I haven't seen him against LHP, but I'm not convinced he can't or won't. hit LHP with the approach he has.
LHP has not been a bugaboo for him in the minors. Worst years have had a ~100 OPS point split which isn't all that dramatic and multiple times he's actually been better against LHP than RHP (including in 2018). I'm not worried about platoon splits for him.
His overall hitting level is what concerns me long term. I just don't think he can hit well enough with passable to average defense to justify everyday time in a corner OF spot. And he does not project as someone who would be useful off the bench if he can't be an everyday guy. Typically I like my bench players to be guys who do one thing very well (defense, platoon hitting, speed, etc).
But we should absolutely give him plenty of opportunities next year to find out. Only way I'd take him out of the lineup is if more promising young guys like Diaz, Mountcastle, Sisco, and Hays are ready and need the opportunity.