Don’t be mad, just wait to buy it till they offer a nice package deal (do we have a patient gamers community here?). If enough users do that, they hopefully change their business model.
Overall I also think that paid add-ons are quite okay, if they actually add new stuff and if the base game is a finished product in itself. Ensures that developers continue to take care of the game without subscriptions and leads to games that one can play for a decade (like CK2). But yeah, Paradox overdoes this.