Yes, of course some FtMs look like cis guys but the OP did say that they don't know exactly why it he doesn't feel attracted to trans people. Of course trans people are as diverse as cis people, but again - attraction is not rational. OP does not know why he doesn't feel attracted to FtMs, but he doesn't and there is nothing wrong with that. If his attraction to a guy fades after he finds out said guy is FtM, that is not OP's fault nor is he to blame for doing anything wrong. It would be a lot easier if it was logical and rational, but attraction just isn't. Some people find some FtMs attractive, some people find them all attractive, some find none of them attractive etc etc. It is not wrong to not be attracted to someone just because of their gender, despite their personality/how they present themselves.
In regards to the mental instability: first of all, yes, you can sometimes tell that a person is trans and therefore should have dysphoria. And if you can't deal with that in a relationship, you are allowed to not be in a relationship with a trans person. If you don't want to date someone because they have depression, you are allowed to not do so. You are allowed to avoid whoever you want in regards to a relationship - whether the reason you avoid them is fair or not. You can't force people to ignore or just deal with their partner's problems if they don't want to. Harsh at it is, you are allowed to exclude anyone you want from dating you. You can't simply tell people to date trans people because they look like cis people.
HRT makes you look different yes, but even those post treatment sometimes look like the sex they were born as. From what I can tell, FtM generally get good results but the fact is that not everyone is going to end up even looking like a guy.
Right, but this is that sticky web of transphobia though...saying umbrella terms like "trans people just aren't attractive" is absolutely ridiculous
And that's cool, because that's not what I said nor is the statement transphobic. It's like saying straight people are homophobic because they are not attracted to their own gender. And no, being trans should not have anything to do with whether or not you are attracted to someone - but it does. Some people just can't deal with that. That's the harsh reality.
and if genitals really don't matter as part of that attractiveness
Again, for some it probably matters more than anything. You are making a blanket statement here by saying that it doesn't matter at all - which for some, it inevitably does.
I'm sure I should have clarified more in my previous post, but you are putting words in my mouth here.