It's worth remembering the huge selection bias (?) when looking at these issues.
Many successful transitioners disappear once finished. They won't come here and tell us how great things worked out. They won't be out and proud in society as trans. They aren't showing up in the statistics, and are essentially invisible.
But many of the people who, for whatever reason, didn't succeed at transitioning are rather vocal about their experiences. They can't always melt back into society, they sometimes stick out, a few might have some significant resentment at the system they think has let them down and cost them years of their lives, broken relationships, false promises and debt, and they want to tell the world about it.
The negative voices are far louder than they should be because the positive voices don't speak up. By looking at this site and the internet as a whole, one would be forgiven for thinking that transition often leads to regret and problems (and life as a sex worker), whereas the reality is transition rarely leads to regret (or sex work). It's all too easy to get sucked down the whirlpool of negativity.
Which brings us round to the point others have made about gatekeeping: there are two types, one negative (therapist wants more money, therapist likes wielding power, therapist is an idiot etc.), but one positive too (therapist genuinely wants to protect his or her patients because he or she mistakenly believes that lots of transitioners end up regretting their decisions.) But it's still gatekeeping, and an overly-protective therapist who is holding back a client based upon distorted perceptions of the likelihood of "failure" is still damaging to the client's wellbeing. While I think we need to separate the two and not throw out the good therapists with the bad, one thing is for certain - there's a huge need for programs to educate therapists in the realities of gender disorders.
We also can't push responsibility away from ourselves. This is, ultimately, our own decision. IC, gatekeeping, whatever. We're the ones taking the pills and going under the knife. Nobody ever forces us to do those things, so the buck stops with us. What amazes me though is the fact that biologically, transition is always a slow process. Hormones don't work overnight. There is so much time for reflection, self-examination, figuring out whether this is the right path for us to take. Regret will not just appear overnight - it'll creep in slowly and most people will see it a mile away and be able to take steps to avoid it (stopping HRT being the obvious choice.) Post-op regret is surely such a small statistic because very few people will have lived in a bubble and really have had no idea that they were going too far by that point in their transitions. When one goes under the knife, it's usually been preceded by a long course of HRT, living full-time in the chosen gender, etc. There really shouldn't be many surprises left.
The regret problem could be solved by slowing the process down and making it more collaborative. Hormones do that already, kinda. The regret seems to arise from people either rushing through the process, or being stubborn and refusing to listen to outside voices who might be telling them things they don't want to hear. I don't see much regret from anyone who takes transition one step at a time and in the care of suitable medical professionals. That's not to say that such care is required by everyone transitioning (and there are some successful DIY transitioners or those who skip certain steps because they've researched their options carefully) - I'm only suggesting that if the goal is to minimize regret, then the standards for care already set out aren't particularly bad.