Abyssea comprises the bulk of the current level 75+ content. It's a set of alternate-dimension (really) versions of a number of zones from original XI, and some of the boxed expansions. Much of the currently desirable "end-game" type gear is obtained in Abyssea via a variety of methods. It's also by far the best place for leveling up; it's not uncommon to gain xp at a rate of 100,000xp per hour if you're there for that purpose. (Note that this generally applies primarily to jobs already at 75+. You can enter Abyssea as low as 30, but your role will be very specific then. Best not to expect to use Abyssea to get your first job up to 75.)
As for soloing, yes, the game overall has become considerably more solo-friendly. It's still not like many other MMOs, but thanks to xp boosts to easy prey mobs, and systems like Fields of Valor, it's not a hopeless struggle like it once was. I soloed dancer (admittedly one of the best soloing jobs) to up to 60 without any real trouble.
The de-facto neogaf LS, StarsOfDestiny, is on Sylph.
If you decide to start up, contact me or any of the other pearlsack holders for a pearl.