Before IPL, India must have been used domestic matches and tournaments to find out the new talents still IPL might have simplified their job, I agree but nothing new in terms of identifying a new talent because of IPL; it has been happening for years. Same way, we cannot say BPL or PCL or any other tournaments are not doing the same. If authorities who responsible on identifying new talent are corrupted then no tournament will help right talented people and IPL cannot be an exception. IPL is big in terms of revenue hence it is setting examples and milestones for other countries to follow.
T20 leagues are good to choose players for National T20 squad only. Right now whats happening in Asia is that those who are performing well in T20 leagues are inducted in ODI and Test squad. ODI and Test is proper cricket and only genuine batsman and bowler can perform there. These picks from leagues are destroying test and ODI cricket.
I am sure the selectors would have checked the background of the selected players. They would know who suits good for ODI and who is better for test cricket. It is not always compulsory that they check their T20 performance. Another issue is there is not much ODI or Test cricket being played and a lot of T20 nowadays. That might be another reason why these new players are being selected from T20 national league.