I still enjoy Rome. It's hard to compare to CK2 and EU4, there is no contest. But when I get sick of CK2 and EU4, I can still sink some hours into EU: Rome to this day. I really like the government and loyalty mechanics. To say it's not playable is an exaggeration. It can definitely feel bland at times, as there aren't many playable factions and most of the map needs to be colonized which requires a lot of patience.
Yeah, I really don't understand how it can be said unplayable. I've just faced two bugs; sometimes it CTD on auto save, and sometimes, display gets weird and I have to quit and reload. Both are uncommon though. The rest is smooth. It inherited a few remnant problems of Paradox games (peace AI is stubborn typically) but there are no real flaws in the AI otherwise. It's hard to get the AI to like you, but if you put the effort, you can still play the diplo game with almost any nation.
I guess I'll get loads of big red crosses for stating this, but I personnaly feel more involved in the character development part than CK2. In CK2, I don't know who are my vassals, nor what they do. Interaction is limited to appointment in the council and civil wars (with it comes revocation). That's almost it for vassal relationships. There are the occasionnal bribes,... but it's uncommon and very situationnal.
In EU:Rome, I manage everything. Councilors matter, but unlike in CK2, they are not just random placeholders for a tech buff; if they have a grudge against me, it might hurt really. Choices are more tricky because several stats are taken in account; add in loyalty, ambitions and managing this and all the governors, military leaders start becoming tricky. It's up to me to fulfil character's ambitions or not, which in turn makes them successful or not socially. Choices sometimes backfire. A good general at first cna hope to become ruler, get loyal units and start thinking of contesting my rule. The regular need to shuffle assignments means I end up knowing characters. They regularly prompt me with demands (I want to lead army X); typically characters I don't want in charge (otherwise they would already lead troops or govern provinces). This creates an interesting dynamyc where refusing makes them dislike me, but appointing them is not something I want either because loyalty and popularity evolve dynamically throughout both the character deeds and mine.
This really contrasts with CK2 dynamyc where everyone is content with their position. Courtiers are courtiers, and fine as is, even a Karling prince in my court won't expect more than not being imprisonned. Children won't ask anything; ambitious ones might ask for a title but repeated refusal is of no consequence, and leading armies,... no one cares. This also contrast with popularity system; prestige in CK2 is just a number with little effects that quickly cap; in EU:Rome, winning a war is a quick way to get popularity (which makes characters more loyal to me) while failing will make characters see me weak, thus more likely to revolt. I'll grant you, managing a large Empire gets tedious and starts feeling micro-management, but getting to that point is really fun.
CK2 also lacks the achievement feel of EU:Rome. Once I'm King in CK2, I've sort of won the game and it's not even really hard to get there. Now however, in EU:Rome, trying to survive as a tribe trap beetween mighty Empires (Rome, Seleucid, Carthage, Egypt or Macedonia depending on where you are on the map and who is successful) is not something easily done.