Def try to join an FC. As you surmise, I think the chat and having others willing to help will ease the burnout.

Although you may decide to main a different job later, adding levels to PLD in the meantime won't hurt anything. The game is flexible in giving people the ability to level everything in a variety (fun also varies) of ways. And the instant you hit Heavensward you can pick up DRK and get it up to continue the story with, or whatever class may hold your fancy.

If an FC is difficult to find, you can also look into just a social LS. Being you're on Mateus, maybe give roleplaying a try? I didn't think of doing it much myself but I took a dive and met some real fun folks and it's a nice distraction from the level grind (in my case, grinding up crafters).