Why does everyone hate Pam?

Most people on this sub hate on her so much but to me her character arc was so wholesome. Seeing her go from a timid, insecure person who never put herself first to a confident woman brave enough to chase new opportunities was one of the best things about the show for me. Sure, Karen wasn’t treated as well as she should’ve been when she was with Jim but again, it was a complicated situation. Please let me know if you disagree.