FFXIV doesn't allow much margin of error when doing fights. Adding a healer who keeps dieing means the tank will probably die during a healing check (ie: swarm), adding an inexperienced tank means the boss may point in the wrong way wiping the group, or the tank dies and adds can't be dealt with. Adding inexperienced DPS can cause DPS checks to fail like briar, hornet, or T7 adds. This doesn't even take into account jobs everyone has to do like avoid petrifying everyone, breaking vines, or lining up during Raff's laser attack.

Farming/clear parties are built for one thing only. They gladly take you if you can do the basic strat and perform a clear without dieing. Otherwise you are just ruining what they were started up for. If you need to learn, start a learning party.