Sexual lust and pornography in Buddhism is considered as being unskillful
One of the ten Paramitas the Buddha has advised to developed towards the path to Nibbana is Viraya which means energy. It is unskillful for the very reason that it leads to a release of energy or a waste of energy which can otherwise be utilized for moving deep into meditation.
Why is it wrong to be primarily interested in a person on a sexual level? If we openly discuss our needs with theirs and being honest with them I see no reason why it is bad?
The way you have put it, it feels like you are talking about casual consensual sex, at the time of Buddha, this might not be prevalent beyond the institution of marriage and the Buddha did not advise the householders to become celibate, He just said, do not indulge in Sexual Misconduct.
Talking about casual consensual sex, born out of sexual lust, the problem is it does not satisfy your lust in any way, the craving arises again and again. You get stuck in a repeated pattern. This in any other situation is just fine and in-fact should be encouraged but if you are seeking Nibbana it is unskillful, not bad as it will not lead you towards advancement as a seeker, it will trap you in Samsaric cycle. Watch this video at 25:50 and see that the monk succumbs to his desire and see what all misery he goes through for that surrender to that one desire. Its the eternal recurrence as Nietzsche put it, and to make it worse, it's nature is only unsatisfactoriness.
Why is pornography wrong?
Pornography actors are basically glorified prostitutes, and making money through prostitution is not Right Livelihoodd. And why is it not Right, because sex involved in prostitution is basically on the physical level, you are using the body of other as an object of masturbation. And it is even worse in Pornography, you are not only using the other as a masturbatory object through your profession you are promoting voyeurism, sex trafficking, poisoning minds of naive individuals.
Drug abuse or depression in pornography must not necessarily be a direct correlation
The actresses have to take painkillers in order to make appear that they are having pleasure while receiving anal sex. Anal sex for anybody is not the way they show in porn movies, also the actors are on steroids for sustaining the erection in that environment where the camera is on you and you are cut in a scene and told what to do and how to do.
Apart from few porn stars who achieved glam, it's not really an industry which won't depress you. Besides all this, we have not even talked about risks of HIV and other STD's.