Its still too early to pass much judgement, quite alot more has change from rome 2 in terms of gameplay mechanics than I was expecting and I'm still getting used to alot of it.
But one thing I will say is there seems too much influence from DeI for my liking. I had respect for DeI as a mod but personally hated the changes. In attila i've spend nearly 50 turns trying to convert one, FUCKING ONE province I have captured to be stable.
it seems like its a end turn simulator now, thats basically all I've done in this game. at least on legendary where I am getting like -30 base public order due to like -14 from immigration.
the unit/building icons look prettier but are more confusing to tell apart. the general/army traditions are displayed in the much better tree format, but don't seem to allow nearly as good customisation as rome 2.
the family pollitics system is cool, but ultimately seems pointless yet again. because there is no net advantage to having higher control on your faction. it seems your better off just letting it do its own thing than actively tried to amass power, like you would in other games like CK2.