Personally I think a lot of juniors from former eastern europe have a mentality problem and they can not produce the same on the WTA tour. It started long ago and the history is full of juniors from the east winning and being presented as future number ones and they never really had any kind of results. Sorana is the best example. Ruxandra dragomir saw in her the number one player in the world and she is outside top 100 and her generation friend Caro is now number 1. Same with Radu - she was presented as number one junior in the world by her coach and in Australia she was nowhere to be seen. I think in the east there is a lot of presure on juniors and they cannot develop properly. Same applies for boys juniors: Mergea, Tecau former number ones never produced anything in the singles. Tecau managed to get into doubles but Mergea didn't manage anything. so I would be more happy to see exceptional players play on the WTA tour even when they are juniors (hingis, Graff , Williams were 16,17,18 when they were winning GS tournaments) than go and waste time on the minor tournaments. If you have value you shouldn't be afraid to go and play on any surface against top senior players.
You are right that exceptional players should play WTA tournaments as fast as possible, but as you said only the most outstanding (talented) players are good enough to have some success there without overworking themselves. Even our current number one Wozniacki started through when she was "already" 17.
I think we have a number of very decent junior players, but of course none of them is a high-flyer. So, it's more than ok for them to start playing ITF junior tournaments and you have to see that they most likely play G2 upwards, the higher rated ones.
All in all we shouldn't forget that a good junior career indicates a certain talent, but is no guarantee for a successful senior career. There are far too many unknown factors. Some of them have a fulminant breakthrough on the WTA, but as fast as they reached the center of attention, as fast the often called tomorrow's stars die down like a sparkling in the rain. Others have never been noticed of during their early career, but almost exploded in terms of improvement when they became older. And there is a group of some players who were decent juniors, but just needed more time to adapt to the higher WTA standards to come back even more impressive like or Alex did.
You are right that many Romanian juniors didn't make the best out of their abilities and potential, especially Sori's latest performances are very disappointing. But she has only been #9 of the year end's junior ranking in her group of age and it seems that she has already achieved more than one could think of her, considering that former junior Top 5 players and junior slam winners like Rus or Flipkens never reached anything noticeable on the tour. But you are right that she degressed and that is really a pity!
To Radu, I never understood why she has been hyped that much. She is not even in the Top 200 of the Junior ITF ranking at the age of 17 and only because she won one or two weak 10k tournaments don't mean that she has to be a future Top Tenner.
It's interesting that you see a connection between East European society and the fact of lost talents, but in my opinion it is only one lesser reason why some Romanian talents couldn't transform their achievements to WTA or ATP level. In contrast to that the three biggest wasted talents or already praised future superstars come from Western Europe (Larcher de Brito, Paszek and Mladenovic), last one because of many injuries, but concerning the other girls mainly because of their attitude and probably environment. Maybe they were burned out or simply lost their ambition because of the thousands of Euros they have earned when they have actually been kids. I think that you are right that especially in Eastern Europe some parents would be ready to do everything to make their children successful sportsmen/women for earning money with them and their popularity. The coaching methods are often doubtable and very hard for the children, so that only the ones with the strongest ambition or the ones who had luck to stay injury free come through.
Keeping this in mind, I would for example say that Wozniacki has a stronger personality than Sorana because she had to practice at least as much as Sori in her youth (knowing her father I would even say more), but is still able to focus and to stand up the pressure while Sori seems to be a nervous wreck at the moment.
In fact every player has another personality no matter from where he/she comes, so generalized claims are not really a reason for the different developments of them. One of them nearly stay injury-free during their early career or even later on, others are walking from one problem to another. Some have a strong personality and are real fighters, others are not and spend their time rather on dispensing the price money they have already won. Some of them find the right coach and good working conitions, others don't.
It's hard to predict future careers of junior players, but from our current junior generation, Ilka Csoregi seems to be most talented and really down-to-earth. Her claycourt abilities are far over the average standard of her age! We will see what she can reach in her further career.