Learn Turkish: Yüksek maaşın yanı sıra, motivasyon da çok önemlidir. - Along with a high salary, motivation is also very important.

While you can sometimes drop the genitive for bare, general nouns, it is required when the noun is modified by an adjective. Because we have the adjective yüksek (high) modifying maaş (salary), adding the genitive suffix -ın is grammatically necessary here.

What is the literal breakdown of the phrase yanı sıra?

It consists of yan (side), the 3rd person possessive suffix -ı (its), and sıra (row/sequence). Because of this possessive construction, it takes a genitive noun before it. You can think of maaşın yanı sıra literally as "at the side of the salary."

Does the da after motivasyon have a special connection to yanı sıra?

Yes, they pair up very naturally in Turkish. Because yanı sıra introduces an addition ("along with X"), using the separate particle da (meaning "also" or "too") on the second subject completes the logic of the sentence: "Along with X, Y is also..."

Why is -dir added to önemli at the end of the sentence?