Camel Archers reduce the damage output of enemy cavalry like Sipahi and Knights, causing unease for Ottoman cavalry.

Spending heavily on Sipahi in feudal can leave Ottomans unable to immediately queue up a counter when they age up, which camel riders can exploit.

Janissaries are the stereotypical anti-cavalry unit you want against camel lancers, because they're not on horseback so they don't suffer from the camel aura, and their firepower does devastating damage to camel frames.

The Mehter provides range defense, which is especially valuable against large archer masses.