Pay attention to the elements and switch characters constantly. Genshin Impact is not a game where one character is played and the other 3 slots are ignored, it just doesn’t work that way.
A majority of the damage in combat comes from combining different elements to create different reactions such as Swirl, Crystalize, Frozen, Melt, or Overloaded. Players need to ‘diversify their team’s elements even slightly and get accustomed to switching between their team of four pretty constantly.