This gunna be long, so buckle up, lol. (Summarization is not my strong suit :D)
Personally, it's my opinion that sex work, on its own, is morally neutral.
We know that sex is a normal and natural human behaviour. Humans are wired for connection and are naturally drawn towards physical contact with others. The reasons to purchase sexual services varies from patron to patron. Things like; stress relief, kink exploration, human contact, engaging conversation, and "mental vacation" are just some of the reasons I've heard. If there are people who are willing to provide a supply for the demand, that's not inherently exploitative just on its own. (From a worker's standpoint, I felt far more exploited while employed by a cafe for just above minimum wage than I do in sex work where I set my own rates and hours.)
I would argue that while sex and human contact can have a therapeutic benefit, it is a far cry from an actual form of therapy. The key difference here being that therapy has a mindfully structured and goal-oriented treatment protocol that aligns with specific methodologies. I would encourage people to do away with the idea that sex workers are therapists. (Even if a sex worker is certified in the field, they may be a therapist, but they not your therapist.) To quote a fellow sex worker on this: We are twice as expensive and half as qualified.
As far as sex addiction goes, there's a mounting body of evidence that suggests it doesn't actually exist. At least, not in the way people think. This is because "sex addiction" fails to activate the same parts of the brain that typical addictions do. It does not appear in the DSM-5 as a diagnosable mental health condition. An interesting fact is that, on average, self proclaimed "sex addicts" do not engage in sexual activities (intercourse/masturbation) more than the general population. The difference here is the internalized shame that "sex addicts" themselves have attached to the specific activity. That shame is often rooted in religious ideology that has been taught to them about sex throughout the duration of their lives. Alternatively, shame can come just from the moral code of your environmental setting as well. One of the growing pains of the present time is that our society still has a lot of contradictory views around sex and around the morality of how we engage with sex. These views are mostly left over from a more puritanical time. It really wasn't that long ago that even divorce was a whispered subject and children born out of wedlock were widely considered as products of sin.
That's not to say that sexual activity can't become problematic. There are many people that engage in sex and masturbation to the point that it does interfere with their day to day life. This is more effectively treated as a symptom of a larger issue, rather than the primary issue itself. It can also be viewed as a compulsive behaviour. The importance of distinguishing between this and a true addiction is that the treatment procedures for addiction vs. lack of impulse control look very different.
As far as trafficking goes, you'd be hard pressed to find someone who doesn't agree that it's a tragic evil. The fallacy with your thinking here though is that labour trafficking exists across nearly every sector. I would not say that there are good reasons to see farming, fishing, or hospitality as "evil" industries because of the trafficking that is rampant within them. Labour rights and legal policies that offer protections based in human rights are essential in actually combatting all forms of trafficking.
I won't get into the "legal and regulated", because I've already written a novel here, but there is a reason sex workers advocate for a decriminalized legal framework. Legalization models sound great on paper but are often counterintuitive and only cause further harm.