The solution that appeases all groups is to leave it the same. This is a two-way door in which those who prefer content over grinding are given access to what they want while those who favor grinding are still allowed to do so at the pace they desire. If both parties can be equally appeased without a compromise then it makes zero sense to eradicate such a system.
I agree with this in principle, but it ignores some basic human nature. One doesn't have to agree with people who find grinding for cap a sign of accomplishment, maybe because it doesn't seem like it is an accomplishment rather than a brainless chore. I happen to find grinding a chore, but I understand the people who feel it is currently an empty feeling to reach cap with so little effort. I wouldn't feel the need to call them names or wish their deaths because they think differently than me.

If I want to play a qualifying round of a sport and my competition doesn't push me my victory seems empty. You can tell me I could just choose to score less goals, or run slower and get a finishing time that's closer to everyone else, but it doesn't change that I know it wasn't a challenge, so I don't feel I won as much as if I was truly pushed to win the competition. Wishing for a greater challenge isn't stupid. The problem here is that some people wish for more challenge and see reaching 50 as one such challenge, while others feel that reaching 50 is not the challenge they play the game for, but instead it unlocks the challenges.

My recommendation? Two paths. One is the existing one where people can grind away in less than one week per class. The other should be something that takes longer due to higher risk, but offering incentive through useful rewards. Level-reactive instances, for example. Behests already adjust the level of the mobs based on a combination of the camp and the members participating, so the means already exist in-game. An instanced XP dungeon could do the same. Get your party together, whatever your level, and head in. Once you enter, the mobs spawn at a challenge relative to your level. Maybe you can even set a star-rating. But also give the player a star rating. I'm talking about a permanent 'badge-of-honour', so to speak. Not an item, but a rating that people can see when they check the player. The more challenges you do, the higher your rating. So when you check two level 50 Lancers and one has a 5-star rating and the other has zero, you have some feeling about how they got there. It doesn't give them better gear. It doesn't mean they're a better player, it's just something that those individuals can be proud of.

Or if ratings aren't preferred, just raise the risk-to-reward ratio in such areas, making them a good place to farm and XP at the same time. Players who opt for the greater challenge come away with more marketable goods, and can better equip themselves and show off that way (though this wouldn't work under the existing market conditions).

In any case, it's important to specifically avoid having unique items in these areas that you can't get anywhere else, because those who do not want the challenge will feel it is unfair that they can't get the items. Unfortunately, when people buy a video game they don't want to be told they can't have something in the game because it's for other people who work harder. Some game designs ignore these people, others (and FFXIV is among them) do not.