A MMORPG is never complete, we always expect more expansions, patches, and updates to add to it. Which necessarily means that the MMORPG industry is in the business of selling incomplete games. Even games that were already huge and didn't have any obvious missing features at launch, like World of Warcraft, have changed since then to contain not only much more content, but also many more features. On launch WoW had a very different UI (e.g. only a single hotkey bar), only half of the content it has today, and all the classes have undergone major rework since. Games with a not-so-good launch, like Star Wars Galaxies, have been completely changed since then (and not always for the better). So if you get into a new game early, you need to be aware that you aren't playing anything close to a final version, and that a final version might never exist.
Like any MMO at launch, LotRO is far from complete. But unlike Vanguard, where the lack of polish was distributed evenly over the whole game, LotRO made sure to make at least the first half of the game polished and more or less complete, and then has content getting thinner in the higher levels. The upcoming content patch Shores of Evendim in June is basically adding lots of level 30 to 40 content, which was previously missing. I would expect future content patches to further pad out the content in the higher levels, before some expansion raises the level cap. I can't see how LotRO would for example add more playable races to the game, they just wouldn't fit in with the lore.
Having this feeling that the upper levels in LotRO are currently low on content is one of the reasons why I'm taking it slow this time. I'm sure there are already level 50 players in the game, but apart from taking a break I wouldn't know what to do at level 50 in LotRO. There isn't much end-game content yet, and the PvP will only get into the swing of things when a large enough part of the population is high enough level to participate on the Free People side. I even prefer to reach level 30 only after the Shores of Evendim are out. I'd rather play other parts of the low-level game a bit more, for example by leveling an alt in a different zone than the Shire.
Now if I was paying for LotRO with a monthly fee, and was "outleveling" the content faster than the developers could add it, I would be angry. But as I paid for a lifetime subscription, I don't feel that I'm losing anything. Have to wait one more month for level 30ish content? No problem, I have all the time in the world. It is not as if that content was actually "missing" from the game, it is only "not in yet". As long as I understand a MMORPG as a work in progress, and not as a product that is final as shipped, it all becomes a question of *when* the content is added, not whether it will be added.