There have been a lot of quality of life adjustments over the years.
-Home point crystals are literally everywhere now. They also function as warp points so traveling around is incredibly easy (once you go through the effort to click on each one to unlock it).
-Lock out timers are no longer a thing once you finish RoV storyline. Assault tags become 10 mins, Salvage, Einherjar, and Dynamis becomes 1 hour cooldown. This allows you to solo a relic or mythic weapon by yourself fairly easily. Still takes a lot of time for a mythic but you can finish one pretty casually in about a month. This is also a good farming method for gil. These events no longer require a party so you can do it all solo.
-Experience points got a huge boost and now there are trust npc. You can build a full party whenever you want assuming you finish RoV to unlock up to 5 trust at once.
-A lot of jobs are completely different now balance wise. MNK was amazing at 75 and during Abyssea but now it's sitting in 75lolpup territory. PUP is a really solid tanking option, BLU SCH and GEO are broken as ***, DNC became one of the top DD in the game, and BRD (yes bard) is expecting a buff soon because Geomancer is so broken it can't keep up. BST PUP and SMN are all very good for different reasons and no longer solo only status. There are even pet focused strats occasionally.(this months ambuscade for example)
-Mounts were added so you pretty much have a chocobo on command for 0 gil. They can't be used everywhere, but they can be used in a ton of areas which makes getting around aggro free extremely easy.
-Monthly Ambuscade allows a lot of gil to be made and supplies a limited time set to be obtained. This changes every month so there is always a large chunk of items to sell monthly. Ambuscade lists a lot of ultimate weapon items which are always in demand and can help you build a weapon of your own.
-There is currently a campaign for Eschan dragons that would be extremely helpful for returning players. The dragons can drop gear from their respective zones and they are dying in around 30 seconds. You don't even have to do anything to the dragon to receives spoils either! This campaign lasts for the rest of the week so I would suggest clearing RoV as soon as possible or at least far enough to access Quetzalcoatl since it drops gear.