I can see your point there. I started my tabletop experience with D&D 3.5e as well as having played and enjoyed a bit of Call of Cthulu for perspective, so I can understand why some people can find D&D, especially 5e (which hampered character customization quiet a bit) a bit to video game-y in regards to leveling up, loot, ect. But I'd argue for a lot of people that can be a draw to it.
Almost everyone plays video games at least a little bit now-a-days, so D&D having a few "video gameish" mechanics can help bring in an easy new comers to Tabletops into the system. I'll even admit, part of me enjoys looking into the books, wiki's, & various other source materials to find new ways to customize my character to better work with my group (or in the case of Adventure League where I don't know who I'll be plying with half the time, which build will make my Fighter most adaptable to a wide variety of groups). Is it nerdy and can it break immersion a little? It can, but I think that's the case only if you let it.
Yeah, it's kind of ironic that DnD's biggest appeal and strength can also be it's biggest drawback.
And all things considered, there are so many games with worse rules than DnD that overall, it doesn't matter that much. Sometimes, immersion can take a bit of a hit and sometimes, the metagaming can run wild, but in the end, you're still playing a well-structured game with easy to use rules.
I'll also elaborate more on a smaller point I made on my previous post that I didn't really go into that well, because it also relates to your point. While the DM is probably the biggest factor for giving people immersion into a tabletop, your fellow players are also a huge factor in that. If your players are constantly holding up the game to pull out a book and spend five minutes double checking every single rule or spell, or saying "according to the book, that monster should have more HP then that", or a player is always running in just the right area where treasure is because they already ran through (or read) the module. Yeah, you get my point.
If your friends are constantly meta-gaming (Which is sadly more common in DnD) then it's going to hurt immersion a bit. This part sort of falls on the DM and other players to tell this person(s) to cut it out because it's slowing down the game and ruining immersion. I think what a lot of people forget when playing DnD is that it is just a game and not every rule has to be followed to the "T" and you shouldn't try to squeeze out every little advantage you get while playing.
It can't be underlined enough how important this is.
Anyone who's ever played a horror game will know how devastating it is for the whole game to have just one guy make a joke at the wrong time. It can easily throw the entire session down the crapper, even if it's just one remark.
A lot of the immersion depends on the players not goofing around too much and only when appropriate. Even in Call of Cthulhu, you can get a few moments were making jokes is ok, but when you do that while the GM is trying his best to create an eerie atmosphere and really make you feel paranoid and in danger... well, it's inconsiderate towards the group and outright disrespectful towards the GM.
Metagaming, too, can ruin the game. Two classical situations are the "Dagger at the throat" or the "hp > falling damage" scenarios, which function basically the same.
Say one of your characters sits in a tavern, drinking ale, he's not wearing his armor. Some bad guy grabs him from behind and holds a dagger to his throat. IRL, that would be pretty fucking dangerous, but when the player goes "Wait, that dagger does like 1d4 damage and I have 50 HP, screw this shit, he can't hurt me even with a dozen slashes", similar with falling from great heights. When the player figures out that he will receive at worst ~40 points of damage while having 50HP, he might decide that he'll just jump down.
That's the kind of metagaming that I really dislike, cause no one in their right mind would just punch someone who's holding a dagger to his throat and no one would casually jump down like 70 feet.
Anyway, speaking of Horror games, has anyone played Eclipse Phase?
Only thumbed through a few rulebooks, the setting seemed kinda weird but also cool, what with the ability to actually have your character die, his conciousness replaced in a cheap body and then proceed with the quest... it's kind of neat, but I wonder how well the rules work out in a game.