I do agree with you, that a first horse on your own should be experienced and forgiving. However, I think the big distinction is ON YOUR OWN... with the help of an experienced trainer, sometimes green or problem horses can make great first horses for riders who have done a LOT of riding on experienced horses and are brave enough to stick it out.
I got my first horse when I was 15, and it was like a baptism of fire. I had been riding for seven years, and riding a variety of horses, not all of whom were schoolmasters by a long shot, and had done a lot of riding of other peoples horses. I had experience with coping with problems like bucking, rearing and bolting, but not with training and managing a horse with these problems. The only reason I got the horse I did - who was not only very spooky, but was a bolter and, when his rider went off balance, would buck until they fell - was because we had a real click, and my trainer, who I knew very well and knew me very well, said she would help me retrain him.
She oversaw all the work I did essentially re-breaking this horse - whilst it was me who spent seven weeks lunging him, doing ground-work and slowly backing him, she would come and watch, or ask me about each session, and was my helper on the ground. Without her, I would never have turned what was essentially a dangerous horse into the most placid dressage horse ever. And boy, did it do wonders for my riding. I never used to be as good as I am now at sticking on, and despite having broken in and started 6 youngsters and 7 'problem' horses (although none quite so bad as him, if maybe just because I've gotten better at it) I've only come off once since I've him. Hitting the ground a lot (and mostly in a nice rubber arena) was actually very good for me, but then again, I'm one of those determined sods to who every fall is a dare to get back on, and I knew that I had the professional backup there behind me.
I'm 21 now, and all I can say is that despite it being really hard, and me meeting the ground a lot in the beginning, he really was the right horse for me, and I was broken-hearted to sell him before going to uni. I actually got offered a job with my trainer thanks to her watching my attitude with him, and since then I've spent my holidays breaking and bringing on young and problem horses for her on her yard, and have been given more and more freedom with them as years have gone on - I broke my first horse on my own, with no input until a few days before the owners came to pick her up, this summer, and I was really proud of the lovely, soft little horse I had produced. I'm far from an expert, but I feel that without that difficult beginning, I wouldn't be where I am now - able to deal with the youngsters in an understanding way that does't push them beyond what they're ready for.
I also wouldn't be enjoying the lovely WBxTB I have now - he was another horse I picked up for nothing, because he was 'difficult to handle', but compared to other horses I've worked with he's an absolute gentleman, and by treating him as though he's a quiet, reliable horse, and managing the few situations where he's difficult, he has become the most relaxed, chilled out and forgiving horse to ride, as well as being talented. Whenever I meet people who used to know him, they comment on how relaxed and quiet he is now. And there's no way I'd have been able to cope with what I now consider his very minor issues if I hadn't had to deal with my first horse's extreme ones.
Basically, (and sorry this has turned into an essay) I think difficult horses (and not necessarily as difficult as mine was!) can sometimes be the making of novice/intermediate riders. BUT, it requires someone who knows what they are doing judging that it is possible both physically and mentally for the rider (some riders would lose a lot of confidence hitting the deck so often) and for the horse to get better, and then overseeing everything that the pair do together. And not all trainers are like that, I know - I was very lucky. But it is possible, but VERY hard work and not even nearly all hugs and kisses - so in general, far better to start with a solid schoolmaster!