Far too often when I check that "join party already in progress" button I get put in groups that have 3/4 completed. If you are not familiar with this.. This means that 3/4 dungeon objectives have been completed. Well 3/4 means that 3 bosses have been downed, and the last objective is to click the exit dungeon button.

WHY WOULD IT EVEN PUT ME IN A COMPLETED DUNGEON IN THE FIRST PLACE.

That is the main reason I do not join groups in progress.. It is coded poorly, and hardly ever repairs the group. The other reason is because... As a healer, I will be replacing a healer who chose to leave his group for whatever reason. Chances are that healer had a good reason to leave the group, so me replacing that healer is a lesson in masochism.

TL: DR Stop asking SE to force good players into bad positions because of your own inadequacy.