I just wanted to respond to this post and this reply to it cos I think it is interesting!
First of all, I want to add the caveat that I do think it's a little unfair to take what is a pithy text post or a random set of replies on a text post and critique it as full-bodied analysis, so I want to make it clear I am NOT doing that. I truly just wanted to use these posts as a jumping off point to reflect common thoughts I've seen all over the fandom.
I also want to note that the original post was made in 2021 and the reply was left in 2023, so generally there may well be context missing from this post that was there once that I am not privy to. All this being said, it just seemed better to make my own post. Lmao.
Anyway. What is interesting about this is that I think the reply is more in agreement with the original than it might first appear. They say that Merlin isn't just 'obsessed with Arthur' but that he 'believes that the prophecies are dependent on Arthur's survival', but I don't think these are two opposing ideas. It can be argued that Merlin is obsessed with Arthur, and that one of the reasons for this is that he believes the prophecy is dependent on Arthur's kingship and survival. And this is because he is told that that it is! Repeatedly! By everyone, pretty much!
But I don't think anyone could effectively argue that Merlin was only interested in keeping Arthur alive. We know he cares about Arthur, a lot, and is concerned not only for his life but for his happiness, and we see several instances of this throughout the show, culminating in his final desperate shout that he can't let Arthur die because he's his friend in the finale. Implying it might just be about duty is as much a reduction of the story being told, I think, than saying it was just because Merlin was in love – if, indeed, anyone is saying either of those things.
And like, yeah, as the commenter says, Merlin does only actively reach beyond that duty and help magic people more directly for other reasons when he is feeling disillusioned with Arthur, which supports the hypothesis of Arthur being his sole focus most of the time.
Merlin being unable to see the Bigger Picture and inadvertantly dooming both Arthur and himself in the process is central to the tragedy of the show, as is the relationship Merlin and Arthur shared throughout it all. Adding a Romantic Love on top of all of that does not have to detract from or stand in opposition to any of that, in my opinion.
What would be really doing a disservice to Merlin's character is acting like his decisions didn't make sense. His decisions were, at every turn, immensely human – a human who was stuck, most of a time, between a rock and a hard place, occasionally with a nest of vipers below him.