Is the essence in our skincare routine is necessary or optional?

Completely optional. Skincare companies use the names like essence however it fits their marketing strategy best, it doesn't really have a specific purpose and it all comes down to ingredients and what skin concerns you're trying to address. If you find a product that you think would be good for your skin - try it out, but otherwise anything that is not a cleanser, moisturiser or spf is not essential.

I think essence is a optional step, the necessary steps are cleanser, moisturizer and sunscreen

Essence is definitely optional! The only necessary steps are cleansing, moisturizer and SPF in the morning :) 💖

Not at all the basic steps in my opinion are : - Cleanser - Moisturizer - Exfoliant - Treatment (depending on your skin concerns) - SPF

I agre on that is a optional step:)