"Celebrate a person" has no meaning to me. We celebrate friendships, events, or occasions. I would ignore this article's use of this.

they are both correct but in this sentence one another makes more sense since it continues with "in our lives" which means there is a bi directional implication. this is given by one another. It means acknowledge any success/accolade to each other.

To "celebrate" another person in this context means to enjoy their presence and offer respect. We often celebrate heroes, people who have done extraordinary things, and talented people such as artists, poets, and musicians.