Can I change the look of my character in Destiny 2?

If you begin the story with your original character, this skips the customization options and goes into into the game.

However, if you do choose to import a character, the game won’t give you the option to customize their appearance.

I had the same struggle when I started Destiny 2, but unfortunately the only way to change the appearance of the characters that were synced from Destiny is to delete it and start from scratch.

there’s no way to edit your appearance once the game starts. This means that once you leave the Destiny 2’s starting screen and customization options, you’re stuck with that look for the rest of the game. If you’re unhappy with your original character’s appearance, it’s best to create a new character from scratch. And if you’re creating a new one, make sure you’re happy with the way they look before moving forward.

Source

If you want to use your Destiny 1 character in Destiny 2, you must use it as-is - you can't customize your appearance. Your only option is to create a new character.