At the end of the day, this remains a motivation issue. These "Monday people" have no motivation to play the game outside of Coil and capping myths. Basically, that is their only goal when logging in to play the game.
I stress again that people should go and find other goals within the game to keep themselves occupied and content. Just like in real life, you won't want to do something that you are not motivated to do yourself. Set yourself a goal, no matter how miniscule, and progress step by step. For example:
- I want to level and play a Warrior.
- I want to level and play a Dragoon.
- I want to get a fully levelled Weaver.
- I want to start and level Carpenter.
- I want to hit 1.5 million gil in the bank.
- I want to craft my own 2-star HQ equipment.
- I want to gather my own materials to make my own 2-star HQ equipment.
- I want to collect a full Battlemage set from Brayflox
- I want to collect a full Cavalry set from Brayflox
- I want to collect a full Infantry set from Brayflox
It's coming up with goals like these, and taking them a step at a time, that keeps the game fun for me. Once again, these are my goals and motivations, they will not necessarily reflect the same for other players. But the point here is to come up with your own in-game goals. Do not restrict yourself to only content that you see ahead of you. I am an achievements sort of person, so I will try to get whatever achievement I can. I set my own goals, and when I achieve it, I am happy.
Someone on Reddit mentioned trying to start a new character, and going self-sustainable to see how long you will last. What this means is, you level all your classes as you do, but when it comes to crafting/buying gear/materia, etc. try and do it yourself. Eg. Your new character has just hit Level 50 on a Paladin - instead of buying the relic weapon and materia off the marketboard, go and level a Blacksmith. While levelling your Blacksmith, if you need materials from other classes (ie. lumber from Carpenter, oil from Alchemist), go and level those classes to be able to craft those instead. To craft your lumber, go and gather your own logs via levelling a botanist. Maybe this is too time consuming for you, but if you have nothing else to do, why not try it. A lot of people just reject "content", whether actual, or artifically generated, on grounds that they may not enjoy it, but how will you know you won't enjoy it if you don't even try it? I once rejected the idea of being a healer, because I thought it would be boring to be a passive character staying at the back and healing, but my WHM is now level 38 and I am actually having fun playing as a healer in dungeons.
Creativity is a key component that many people seem to lack these days. A lot of people follow the standard rat race to 50, doing the same thing everyone does, then complaining about the same thing everyone else complains about. Try breaking out of the mold, and being different.