I like Arcanum DESPITE its combat and due how reactive the world is to the player's character (and how expansive the character creation is, compared to most cRPGs). Like you said before - just because combat is not great and the game was obviously unfinished doesn't mean it can be considered a great RPG in spite of these flaws.
The thing with combat is that oftentimes it is the key aspect of a game's actual gameplay. Arcanum's combat is so bad that it pretty much disqualifies Arcanum in my eyes. And don't think this is because I am a combat fag, it's just that I requires good gameplay in a game that I play. Disco Elysium had no combat and I thought it was great, because the thing that you are constantly engaging in is so fun and engaging. This is also why I love a game like Vagrus or Sunless Sea. Planescape: Torment is one of my favorite games of all time, not because the combat is good, but because it's okay enough that I can actually enjoy the things the game does good without wanting to drive a spike through my brain. KotOR is the same thing. It's like a minimum threshold you have to meet in regards to how good the combat is in the game (that threshold doesn't even mean the game has good combat, it just has to not suck so hard the game is totally unfun to play) in order to even be in the conversation of whether or not the game is good.
I found combat to be fine in Fallout and the writing was serviceable. This sounds like a personal preference more than anything else. Not that there is anything wrong with that (after all, de gustibus non disputandum est), but it can't exactly be used as an objective criteria when weighting one game against the other.
You say it's subjective, but it's not. Fallout's combat system is objectively simple and easy. If you're okay with that, I'm jealous you have a lower bar than myself when it comes to the type of combat you can enjoy in games, but when it comes to weighing games against each other, I do think we can hold Fallout's simplistic combat against it. Also, while you might say the writing is serviceable, I'd argue Baldur's Gate had fantastic writing. Note, I wasn't stating that Fallout is a bad game (that is on the table though, but I am not going to get into that now), merely that Baldur's Gate is a better game.
I didn't have any problem with either the art style nor the UI, so I am not sure what's the problem here. Nor I find it to be an argument for or against something being a particularly good RPG.
Again, even if I was to secede the point that Fallout's UI and art style were not bad, I would argue that Baldur's Gate's art style and UI are far superior to that of Fallout, hence, making it the better game, which makes it the better RPG.
I disagree with this take.
It does matter how many RPG elements a game has (or how they are implemented) if we are to judge it as an RPG. For example: I will take any Troika game over a BioWare game, because in Troika games low intellect actually impacts what you can say, whereas in BioWare games you can make a character with INT 1 and talk perfectly fine as their games don't track character's stats in conversations. Which is VERY stupid thing to do in an RPG.
And this is the crux of our difference, and it's honestly a take that blows my mind. If Troika made a game with shit combat, shit writing, and shit art style, but kept the system in place where the game tracks the characters stats in conversation so your character with low INT will act dumb, you would prefer that game to a hypothetical BioWare title that did everything right but didn't have that one feature? I'm almost certain you would say that's ridiculous, which means that there is a point where the quality of the game supercedes the amount of RPG elements a game has, as long as both games have enough of said elements so that they are both considered to be a part of the RPG genre. That means we just disagree where the line should be drawn, and to that I say, any line that you draw will be entirely arbitrary, and it will fall apart under intense scrutiny. At the end of the day, we're playing games here, and what matters the most is whether or not a game is fun, not how many RPG element buzzwords the game has in it.
EDIT: Oh and even more than the combat, the thing that sucks about Arcanum is how broken it is. I could not get it to run properly on my PC, and the bugs. The game was even worse on release without all the patches. Like I said, disqualified.