I've played MANY MMO's and RPG's and while XIV's early levels aren't great, they aren't the worst.
If anything, the MSQ helps detract from the fact that actual combat at those levels is utter garbage due to the ridiculously long GCD, the complete lack of skills and terribly spaced skills (DRG gets the start of their 2nd combo at level 6. The second part of it comes at level 38 and the 3rd part of it comes at level 50!)
Much of XIV's early gameplay, i.e. levels 1-50, would be much improved from an overhaul of skill distribution, if they could frontload more of a jobs overall skills into this level range to not only make the leveling experience better, but also mitigate the awfulness that is syncing down to having no skills available...
With some minor tweaks to the patch MSQ from after ARR and before HW to cut down on some of the waffle that goes on there...
Actually, these days it's entirely the other way around. Current day MMO's are almost all unanimously focused on the "Get end game NOW!" style of play, with gratuitous experience gains, heavily streamlined quests and leveling progression, XP boosts upon XP boosts upon XP boosts etc.
It's one of the things that helps XIV stand out, the fact that it ISN'T just about getting to max level and that the Journey itself can actually be interesting and fun - Mostly if you care about the story.
Of course, much of this falls apart after you've leveled up your first job via MSQ and then you're left with 14 (Soon 16) other Jobs to level up and nothing but Duty/Deep Dungeon grinds to utilize... Since once you've done the MSQ, all that's left to do with other jobs is whatever end-game grinds are available (Such as Relics or farming out gear so that you can... Replace better gear when the next patch/expansion comes out)
Still, that initial leveling experience that comes with the MSQ can be a fantastic journey, one that many modern MMO's miss out on because they're overly reliant on ensuring that even newbies can get to "Relevant Content" by way of leveling up to max level as fast as possible and skipping much of the Gear Treadmill to get right into the newest content.
Which can be a fine way to make a game. There are many people whom might be burnt out on a particular game and want to quickly get back into their normal routine of end-game farming in a new game and thus, an MMO that focuses on enabling people to rush through is ideal for them.
However, there's something to be said about having MMO's where the Journey still retains that feeling everyone once had when they played their first MMO, where the goal was just to experience the game and have fun, before everything became about end-game farming, maximizing DPS, Raiding, Spamming mindless dungeons for currencies to purchase loot upgrades...
Since, end-game farm fests are a dime a dozen. There's a plethora of MMO's on the market with bunches of end-game Dungeons/Raids to farm out. Many of them flat out better than the meagre offering that XIV provides (Given it's so-so combat and clunky spaghetti codes)