Cliff notes: XIV is incomplete. Just a fact, not defending either side.

In XI the grind was worse. I mean 5k/hr was good for a looooong time before Cop/ToAU. You had to rely on making an a good party that consisted of good damage, a tank, good heals, and mp conservation. Job roles were specifically defined. Whm? You buff/heal. Blm? You nuke and sometimes debuff. Rdm? You debuff/cure/buff. As a mage you attempted to get as much +healing mp gear, mnd for you cures/slow/para, int for you nukes/debuffs. As DD you tried to get as much attack/acc/str/dex. As a tank you tried to either blink tank or reduce dmg you take; in both cases you tried to boost enmity. Killing mobs took more than 1 minute in most cases and if you killed in under two minutes you were probably still getting good xp/hr. Killing a mob was, for the most part, rewarding for the amount of xp you got and the faster you killed the more xp bonus you would get for chains. You had to coordinate SC's between DD and any mages for MB. Although the grind was worse each new level you hit usually opened up a new piece of gear you could wear or a new spell/ability you could use. These new spells were, for the most part, far better than previous spells. Hitting a new level was almost always 'awesome'.

Outside of partying, or even while LFG with your flag up, you could craft, harvest, farm, build fame or even do some quests. With your HP set to Jeuno(or later WG), and a warp scroll/blm sub handy, you could instantly for 'free' teleport back to town to join a party if you got a tell. You could also spend time hunting some NMs. Remember that bird in West Saru with the +hmp wand? You only needed to be level 10~ to kill it. Leaping boots, emp pin, that signia, the list goes on and on of NMs that were rather low rank that dropped good gear. Some of that gear potentially lasted until level cap or at least long enough that the time you spent camping was well worth it. Switching jobs instantly converted your stats so by playing WHM you could still have the full benefit of playing WAR by simply changing jobs and equipping different gear. Transportation was cake once you hit 20 and were allowed to rent chocobos from the cities and the crags. Shouting for a 'Teleport-Mea' then picking up a choco from the crag wasn't a bad run to Windurst. Once outpost teleports were added the game got even easier to get around in. Being able to set your HP was paramount to saving time. All of the above was possible before hitting the level cap or even level 50 for that matter.

In XIV you're missing a good 90% of the above.
-Job roles are not defined, although 'jobs' are coming so we'll see how they turn out. Any melee for the most part can tank when mobs die so fast so long as you have some heals to back it up.
-Gear is no where near as important as in XI. Stats are pretty much a joke at this time. Spending hours camping that sheep in coerthas for that mage body will give me no visible increase in damage or accuracy of spells. There is no reason to aim for top of the line gear except for 'looking cool'.
-Grinding is terrible. Mobs die so fast that there is no sense of 'reward' for killing one. Mobs really aren't difficult. While Sp/hr is potentially higher the 'bore' factor is exponentially higher. I personally can't grind for an hour on mobs for 20k sp. If fatigue hits I just leave the party. There are no SP chains to make you 'want' to kill faster to keep the chain going. Mobs usually repop slow in regards to their kill time.
-Ranks are mostly meaningless. Don't get me wrong, there are a few ranks on the way to 50 that you can't wait for to pick up certain skills(sentinel, siphon mp, sac+cure 3, etc). But compared to XI, as conj you start with all your tier 1 nukes that do the same damage. You hit rank 24 and you get tier 2 nukes. For more mp these basically do the same amount of damage and are on a longer cooldown. There is no 'reward' or sense of accomplishment. Tie this to the fact that ranks 1-20 are literally a breeze.
-Strategy is non existent outside of NMs and even there its hardly required. BRs consist of people randomly queing up their abilities, standing idle for 10s while everyone joins, and then just using a normal ability for a little bit more damage. There's no skill required to do a BR. SC's made you focus and time attacks.
-Transportation/traveling. Limited anima makes traveling a pain. You can't set your HP, instead it's fixed to the last aetheryte you touched. This makes return rather worthless plus it costs you 1 anima. There are no 'teleports' or 'warps'. Seamless zones make for less diversity which makes for a boring time running through the same scenery all the time.
- While I did argue that stats are rather worthless, they do make a difference to a certain point(40-60 in a stat). Going 'all out' on a certain class makes you 'gimp' for ranking other classes. As an example I have 150 vit/pie for my 50 thm with everything else at base aside from mnd(31~). When I pop on glad I totally suck. When I play my conj my nukes blow. Assignable stats limit the 'potential' of other classes. If we assigned each class their own stats that saved it'd be a different story...
-Content. Not much to do outside of leves or crafting/gathering. NMs are not soloable unless you're 50. No real gear to grind for to make you 'better' for parties. Most sidequests are mediocre at best with a few being actually good.
-LFG. Doesn't exist. Nuff said.
-No D box!
-latency; blows

I'm sure I've forgotten some stuff but this seems to cover most of what I see the game lacking(which is almost everything lol). It's easy to see why people always refer to XI being 'great' compared to XIV. It had a system that worked even if it didn't allow you to 'solo' your way to level cap. I'd be much happier with mob difficulty increased dramatically and giving the people that want to 'solo' a campaign style way to level to 50 if they don't have time/don't want to party. Leves are a nice way to SP if they'd just balance the SP you could get for them all(they all need to give you 9~k sp minimum with a 4-way link without GA for rank 30+), and they really should make everyone get the same leves each reset so linking would be very easy.

With the current state of the game we really need to wait till the end of the summer to see where the foundation of the game stands and then make our judgments. Until then it's just a bitch fest of what should be and what we want. If SE can deliver us a system that mimics that of XI's I'm pretty sure 80% of the playerbase would be very happy.