This is mostly just food for thought, and spoiler answer: No, but its real close.
To really answer this question, you first have to ask yourself what you value most in an MMO, and how many of those factors does a game have to have before we can label it an MMO in the traditional sense.
Let’s start with the easy stuff.
Massive: A large number of players need to be around, more than a large FPS map or private Minecraft server of 64 or 128 players.
Multiplayer: Not only must a larger number of players be around, but that should mean something critical to the game. If you can get 90% or more of the experience without interacting with others, the game fails here.
Online: This one is interesting, because at first you think this is simply about connecting to a server, but does asynchronous activity count here? Or does ‘online’ mean two people are online and interacting in real time? A dungeon run is real-time, you selling something on an auction house is asynchronous. How much of the core gameplay needs to be real-time to count? Does it at all?
Let’s look at how I play CoC/BB. I run a ‘clan’ in both, the CoC one has 50 accounts, the BB around 30. In both games we have regular, guild-wide activities (Clan Wars and Operations), and in both of these activities we spend a solid amount of time helping each other out and working together to win. One is group-based PvP, the other is group-based PvE. Chat is very frequent and lively, and Reddit/YouTube is often referred for strategy or game updates.
Personal and guild-wide progression is a main focus of both games, and both games are frequently updated, often with content that adds more progression. Both games are played by millions in one ‘world’ (you can potentially interact with anyone playing), and minor solo PvE content aside, everything is multiplayer.
Basically, the way I play CoC/BB is more like playing an MMO than how I play FFXIV today with my wife, where we duo almost exclusively (random fate groups and dungeon runs aside). I’m more invested in CoC/BB, I’m more into the community of those games, and I do more massive, multiplayer, online gaming in those titles than in FFXIV.
Again, the biggest disconnect is the asynchronous difference, and the lack of a true ‘character’ to play in CoC/BB, although that last one I could argue is no different than flying a ship in EVE. In CoC/BB I’m the chief (pilot) of my village (ship), fighting against other chiefs (pilots) and their village (ship)*.
*Insert easy TiDi is asynchronous gameplay joke here.
Hardcore Casual 
Does this mean your search for a successful F2P MMO is over? ;)
That said, it seems clear that CoC and such fail on the world part. No world, no MMO. In fact, I would even hesitate to include lobby-based games (like Dragon Nest) under the MMO umbrella. You can “interact” with potentially anyone in CoC, but the same could be said for Yahoo Pool. Is Yahoo Pool an MMO? I’m sure there are clans out there, tournaments, and people sharing Youtube links in the chat interface there too.
Yea, world is a big miss for these games, but at the same time how much world does WoW have when everyone is inside a garrison 90% of the time, and the other 10% is when they get teleported into a dungeon with randoms? How different is the very quick questing game to the equally quick and just as challenging/unique solo goblin campaign in CoC? Both feature ‘zones’ you forget as soon as you see them, both are done solo, and both are something you ‘get through’ to hit the ‘real game’.
The lack of a “true character” to play doesn’treally factor into wether something is an MMO or not (unless you take that to mean MMORPG specifically, which is fair enough too). If we are simply talking wether or not they are MMOs they absolutely are. I dont think synchroneous gameplay is a requirement.
Minor stuff aside, still a good point. You are easily more engaged in the communities in CoC/BB than in many modern MMOs, but you dont HAVE to be, so i guess that just puts them on par with mmorpgs
Shandren out
I’m trying not use the term “MMO” much any more. It’s far too wide-sweeping and doesn’t really convey much in the way of meaning in most discussions. I try to use “MMORPG” for clarity but even that isn’t great.
Personally I’m primarily interested in what I guess could be loosely described as 3D graphical DIKU-MUD variants but that’s a bit of a mouthful.
If you sold me an MMO, and I opened it up and found CoC, I would be very disappointed. I feel the same way about calling calling WoT an MMO. It’s basically stripped down DotA with tanks, so is DotA an MMO as well? Is any game with multiplayer and a chat function?
The fact that WoW has had a bad case of world rot to the point that it turned into a glorified chat lobby with mini games doesn’t change this. Maybe we should revoke their MMO card instead?