Getting spears out forces Ottomans to not go for instant Sipahi and might push them into archers instead.

You typically want to go range Jeanne against a civilization that might want to trade with cavalry, because then you're able to snipe out the cavalry. Not the case against Ottomans here, so going melee Jeanne with your own cavalry play makes sense.

Once Ottomans reach Castle Age they become an entirely different beast with Janissaries, so there is urgency for Jeanne d'Arc to be present and dangerous in Feudal Age.

You need to prioritize archers to snipe Imams; if you can't snipe them out immediately you'll lose long-term. You only need about 12 archers to one-shot Spearmen.

There's still the Great Bombard; that's why you want Bloodlines on your Knights, so the Great Bombard can't kill you — it no longer does bonus damage to cavalry, only infantry.