When we move from a monogamous to a non-monogamous context, sometimes the contraction of our dating pool can make it feel like the most important compatibility issue is just "are they also non-monogamous?" when in fact all the same standards we applied in monogamous relating should probably still be in play. What do I mean by this? I mean:
Do you have similar values?
Does this person make you smile?
Do you have enough similar interests to want to spend time together?
Do you want to spend a similar amount of time together? Do you think of relationships in a similar way? (Maybe that's a value? Values mean different things to different people.)
Do you have compatible feelings about family? (is it a deal breaker that they do or don't want kids or that one of you already has them?)
Does one of you intend to move soon or travel a lot in a way that might complicate the relationship you're forming?
All this before we even get to the possibilities of incompatibility that are uniquely polyamorous problems, like one person preferring a more kitchen-table style of polycule interaction and the other wanting a parallel relationship to their metamours; or someone coming from a hierarchical background while the other is pretty firmly egalitarian in their relating. Do we have enough energy and bandwidth to make the relationship we've agreed we want without neglecting existing partnerships?
That is, it's a lot more than, "they're cute and also not exclusive, of course we'll date!" if we want the dating to go well. It can be really easy to get caught up in NRE and ignore points of incompatibility, especially incompatibility about things like bandwidth, time, and polycule interaction - so choosing to be intentional and accelerate connections slowly can help to not "run off a cliff" with NRE or not find that suddenly you're accustomed to a large amount of time with a partner that there aren't enough shared interests to sustain as the new relationship energy fades.