Despite being somewhat simplistic compared to other Paradox games at release (while simultaneously being rather too complex for many strategy gamers coming from the likes of Civ), Stellaris, for all its flaws, did have a few advantages going for it to set it apart. The procedurally generated galaxies - where that race of mushroom people or penguin people or floating bag of fart people could be an entirely different empire in culture and personality every time - as well as the empire customization made it quite special and different. I:R, by contrast, just kinda felt like several random aspects of CK2, EUIV, and Vicky 2 mashed together - I didn't mind I:R (though I understand if people were disappointed), but it was kinda just "okay" to me at release.
Crusader Kings, by contrast, does have a number of things to set it apart, mainly the heavy character and roleplay focus.
Plus, Stellaris' DLCs have generally been very good. The story pack + expansion system works very well for it, and I think it will work well for CK3 too. There was an excellent thread on reddit a while back discussing why Stellaris' DLC model and EUIV's DLC model, despite appearing similar on paper, had much different receptions, with Stellaris' being the superior model, and it boiled down to new features and game mechanics being included in the base game/free patches for the most part, and I think judging how I:R seems to be going that route, that CK3 will also be the same.
Even the pre-Stellaris launches were godawful, it was a miracle that Stellaris actually ran okay at release.
And who can forget the fiasco that was the buggy mess of Rajas of India? I was around then and I remember the great and mighty flamewars waged against the devs by angry players on the forums.