I was disappointed by Stellaris too, and I can understand if that influences the purchasing decision of a prsoecptive buyer, but just keep in mind that even though both are Paradox games this game has a different designer. Johan is the lead behind this game, and was also the lead for EU4. He has a track record of consistently delivering really good grand strategy games, at least in my view.
EU: Rome was a direct adaptation of EU3 for ancient times, and this one is more of its own beast (which I suppose is one reason they didn’t name this EU: Rome 2). Imagine the core gameplay loop of EU4 coupled with a lite version of the CK2 character management / internal politics, and more detailed population management.
If you decide to pick it up, you can trust that at least Kevin and myself will be around to read and write numerous posts about it during the first weeks of release!
Speaking of, @KevinC you got a first game in mind? I am eyeing the ‘Hispania Universalis’ achievement (form Greater Iberia) and thinking of starting out as a small Iberian tribe. The early game should be exciting with many tribes around to conquer, and the mid game boss is there in the form of Carthage. The mechanics for Republics look very interesting so I may go for one of them on the second play through, perhaps even (gasp) Rome itself.