Here\'s inspected source code
input aria-label=\"Phone number, username, or email\" aria-required=\"true\" autocapitalize=\"off\" autocorrect=\"off\" maxlength=\
Observe that while open instagram homepage, it shows spinner on login form for few moment and then display the fields. So your need to manage synchronization in your script.
Use explicit wait in your code until desired field get ready for interaction.
username = WebDriverWait(driver, 20).until(EC.visibility_of_element_located((By.XPATH, "//input[@name='username']")))
username.send_keys('username')
password = WebDriverWait(driver, 20).until(EC.visibility_of_element_located((By.XPATH, "//input[@name='password']")))
password.send_keys('pw')
Need to import below packages
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC