So what is good for us to recognise, is that different people think differently, so what is or isn't immersive is rather subjective. Personally what I find most immersive is LARP, where there are really no rules at all, just pure inhabitation and representation of character, followed by relatively rules light tabletop RPGs with simmish logic (i.e. the rules merely represent diegetic concepts) where it is mostly just freeform roleplay with occasional quick rolls.I've personally been in a much higher frequency of "writer's room" situations when playing D&D than I ever had with the roleplaying games that detractors told me should be breaking my in-character immersion or roleplaying. Same is true for many of my players.
What I find unimmersive is when the decision making process of the character and the the player get diverged, when I as player need to decide things the character doesn't. With quantum gear and flashback Blades has quite a bit of those, and the at least to us the resolution mechanic often requires more OOC pondering than simple D&D skill checks would. Not that D&D (any edition) is really optimal in this regard either, as they are relatively crunchy systems and fiction to rules connection is sometimes unclear. But basic out of combat, "do stuff, perhaps roll some skills" gameplay is pretty smooth.
It is probably due my LARP background that I am not terribly fond of ruleifying certain things, as I feel that when good immersions and expression of character is going on, people should be just allowed to do their thing and the rules should not get in the way. For example I utterly hate rules that tell how my character should feel, as that is for my internal mental model of the character to decide, and if rules conflict with that it is one of the most immersion shattering things I know.