#1 is SE's poor design choice. It's in place because you can only do quests your level or under. I'm guessing they didn't want you to accept and complete a quest on a higher level class, then switch to your low level and hand it in for massive exp. But essentially it ends up working more like, my low level sees a quests, accepts and completes it, only to find out I can't hand it in for another 3 levels. Annoying as hell when you're leveling.
#2 They only want to give quests every 5 levels and seem to kick and scream against anything in between. As the game is now it's almost pointless getting your class gear at level 50 unless you're brand new and this is your first class. If you have a higher level class, chances are you already have a better set of gear crafted or bought with tomes before your other character even hits 50. But at least we have Vanity now.
#3 Oh you're just starting to know the frustrations of the Chocobo system. You can't talk to NPC's while mounted. You couldn't go into a new zone while mounted, but they changed it so it auto-dismounts you. Why you can't just zone through without dismounting, then appear on the other side walking if its in a town, or still on your chocobo, I have no idea. If you summon your chocobo it counts as a party member, so you can't do quests with one out, or queue for a dungeon with one out. Even if the timer expires, it somehow still counts as being in your party and you have to un-summon it before you can do anything. There's more, these are just some of the more common chocobo problems
#4 I'm not sure the issue you're having with crafting, but I'm assuming you're having trouble changing classes. Did you know after you save a gear set you can put it on a hotbar so you can just press the button and switch? No messing around with the character menu, this is as easy as you'll ever need it.
#5 The latency issue is because of SE's weird obsession to have everything, and I mean EVERYTHING synced up to the server. Most MMOs calculate all avoidable AoE damage, movement, etc on your own computer so even if you have a slower connection or lag, if you dodge it on your computer you'll end up dodging it in the game, unless you have VERY bad latency. How it works in this game is when the enemy does a cast time, it starts on the server first. If you have latency, you'll see it later than it actually registers in the server. Even if you dodge it, on the server it's shown to have already gone off before you even saw it. To make it worse, your movement isn't registered until the information reaches the server, making it two times as bad.
For a better explanation on the problem, check this out
#6 I was gonna say it'd load faster on a SSD but you're running it off that, so I got nothing for ya there. I run it off a PS4 and it's actually faster loading (by a bit) than my PC was. Sadly I doubt they'll ever remove the loading points between maps. As easy as it seems, it's not all one large map, they have to make a new map and import all the current ones, the fill in the space between, or something, idk. I think they did this so they could have the game looking as good as it does without requiring way higher specs. And of course, I'm sure the PS3 limitations were part of it.
#7 Back in 1.0, the game didn't even have jumping so I guess invisible walls weren't even an issue then, except maybe if you wanted to try falling off a ledge or something and couldn't. I don't think they're adding any flying mounts ever, so they won't get rid of most of these. But there's no reason they can't remove some of the minor annoying ones, where you could use a spot as a shortcut or something. I came across one absolutely absurd invisible wall. I jumped up to a rock and was able to walk across the entire thing, but there was a small rock wall beside me. I tried to walk up to it, but halfway across this flat rock and the rock wall, there was an invisible wall for absolutely no reason. Messed up lol.
By the way, to get around the absolutely stupid 1000 character limit, just copy your post, cut all but like the first sentence, then use the Edit feature and paste the rest back in there. It'll bypass it.