Yes it is a spiritual successor to BG2 and if you add some story elements and some more budget it could have been called BG3.
I suppose that depends on what you liked in BG2 and what BG2 was for you. I have a soft spot for Pathfinder and even backed the sequel as I think company has a heart in the right place, but that said, from what I played I thought Kingmaker was pretty bad. As a spiritual successor to BG1 - I might see it. As a successor to BG2 - definitely not.
I do not think PF wanted to be a spiritual sucessor of BG, I think they wanted to make a "Pathfinder TT" videogame. It is known that many of the Owlcat´s devs are Pathfinder "nerdys". When the time came to make another game they chose another Classic AP of PF1e: Wrath of the Righteous adding more mechanics of the PF ruleset: Mounted combat, Mythic paths, etc.
I mean, the game is the classic AP "Pathfinder: kingmaker" of Paizo, with all the rules of PF1e and the features and classes of the PNP campaign, like the kingdom management, NPCS, Story, even the difficulty spike in combats and skillchecks... with many improvements.
And if you played the original campaign you can see they made a very faithful depiction of the campaign and the feel of the experience of playing PF in a videogame. Kudos to them.
