It's not just about having the power...

[Ibrîniðilpathânezel]

It is true that the Valar regretted the War of Wrath and the destruction it caused to the lands of Middle-earth, but it is also true that Eru felt that this situation could have been avoided if the Valar had dealt with Melkor much sooner, rather than allow him to have so much free rein in ME, both before the Elves awakened and after. I have done a lot of reading and research in all of the books, including the Letters and HoME books, but I haven't read through any of them recently enough to remember precisely where these references are. *sigh* I know where most of my copies of the books are: buried in my office, all too literally, so I don't really have access to them right now. As soon as I can get at them, I must read through them again, 'cause I can remember many things, but can't tell you exactly where it appeared. *double sigh* They say the memory is the first thing to go, and they may be right....

Now that said, in one of the few books I do have access to (UT), it is said about the Istari and the fact that they were sent in humble human forms:

"And this the Valar did, desiring to amend the errors of old, especially that they had attempted to guard and seclude the Eldar by their own might and glory revealed; whereas now their emissaries were forbidden to reveal themselves in forms of majesty, or to seek to rule the wills of Men or Elves by open display of power."

The error, from other references I recall but cannot quote (at the moment), was twofold: that the Valar used a display of power to influence the Elves so that they would come to Valinor for protection, and that they had put off a final confrontation with Melkor for so long, such seclusion was (at least in their minds) necessary. This was not what Eru would have wanted; he would have preferred for the Valar to trust him to safeguard his Children while Melkor was dealt with (or better, deal with him before the Children awakened). They didn't, and they made mistakes in both the use of Authority and Might.

I REALLY need to get a bulldozer and clean out the years of detritus that have buried my office....