That's only natural and is the case for every MMORPG ever, and will always remain that way. The longer people play, the more the average level will shift to the upper end, which means that's where the content needs to be. So of course content will be centered around end levels. And the longer a MMORPG lives, the more content will be released for said levels. So if a MMORPG is around for as much time as FFXI has been, a bulk of the content will be designed for high level players. Now the development team has to ask themselves what a person wanting to level a new job will want: do they wanna spend weeks of grinding it through all the levels again like they did five times before? Or do they want it because they saw someone else play it at 99 and thought it could be a fun job? Or maybe even useful for an event?
If it's the latter two, they won't be able to play it like they want to unless they go through weeks of torture. And it gets worse the longer the game goes on, because the higher the average level shifts, the less people will be willing to EXP, meaning it only gets harder to get there. EXPing now with the previous system would be next to impossible because almost everyone who wanted to level a job has leveled it. And casual leveling of another job wouldn't happen, because it wasn't worth it unless you really planned on fully utilizing that job.
Quote by a Lv75 career SAM who just got Byakko's Haidate: "Wiki says I can self-SC with Meikyo Shusui, but I don't have that WS."
It definitely is harder, because the infrastructure is worse. That's not a bad thing though. If you can't find five people to level the way you want, then it's a good thing SE removed that option, because obviously it isn't popular.
First, wanting to level up quickly does not equate to wanting to finish the game as quickly as possible. If people wanted that, they wouldn't be playing a MMORPG. Second, the majority of EXPing did not happen within a linkshell. It was either shouting or flagging up and waiting for random people to invite you. Sure, LS parties did happen, but that wasn't where bonds were formed. It was during static mission groups, doing events daily with the people around you, talking to them regardless of what you were doing, even if you never saw each others' characters. There are still linkshells that have been around for years, and there were a myriad of linkshells that dried out and disbanded within weeks. The only reason you notice it more these days is because the population in general is lower.
Then you expect something entirely unrealistic. Take a look at FFXIV. Why do you think anyone at all kept playing after that disastrous start? Because they knew the game was going to change. They saw something was worth staying for, and trusted that time would fix the rest. That is the true nature for every MMORPG, they all change with time.
Completely wrong. You cannot get to the end quickly. You can get to the end of EXPing quickly. But the game does not consist of EXP, it never did, and it shouldn't be. EXP is the first step of the journey, and it's one of many.