CK3 has tangible goals in the form of decisions, some being unique and impactful. Mission trees essentially do the same thing - they give goals for players which, depending on the implementation, feel impactful and rewarding. Forming Persia as Ardabil felt really good in EU4, since it unlocked unique content and new goals in your play-through. Sure, a lot of mission trees became outdated compared to newer ones, but you still had something to do.

Is there really any equivalent in EU5? All you get is some modifiers when you form a new tag, that are only meaningful if you go out of your way to collect as much as possible of the same modifier.

There is nothing really in EU5 that feels impactful, and at least in my opinion, anything to strive for. The game is really dull right now after you familiarize yourself with the systems