[Raynor]

Originally Posted by alatar

That's funny, as it never was safe before nor afterwards.

In what sense wasn't it safe?

Can never see Melkor for who he really is.

I presume you are reffering to his release of Melkor:

Originally Posted by Osanwe kenta

The weakest and most imprudent of all the actions of Manwe, as it seems to many, was the release of Melkor from captivity. From this came the greatest loss and harm: the death of the Trees, and the exile and the anguish of the Noldor. Yet through this suffering there came also, as maybe in no other way could it have come, the victory of the Elder Days: the downfall of Angband and the last overthrow of Melkor.

Who then can say with assurance that if Melkor had been held in bond less evil would have followed? Even in his diminishment the power of Melkor is beyond our calculation. Yet some ruinous outburst of his despair is not the worst that might have befallen. The release was according to the promise of Manwe. If Manwe had broken this promise for his own purposes, even though still intending "good", he would have taken a step upon the paths of Melkor.

This, of course, leads to all sorts of other problems.

Originally Posted by Notes on motives in the Silmarillion, iii, Myths Transformed, HoME X

But, if we dare to attempt to enter the mind of the Elder King, assigning motives and finding faults, there are things to remember before we deliver a judgement. Manwe was the spirit of greatest wisdom and prudence in Arda. He is represented as having had the greatest knowledge of the Music, as a whole, possessed by any one finite mind; and he alone of all persons or minds in that time is represented as having the power of direct recourse to and communication with Eru. He must have grasped with great clarity what even we may perceive dimly: that it was the essential mode of the process of 'history' in Arda that evil should constantly arise, and that out of it new good should constantly come. One especial aspect of this is the strange way in which the evils of the Marrer, or his inheritors, are turned into weapons against evil. If we consider the situation after the escape of Morgoth and the reestablishment of his abode in Middle-earth, we shall see that the heroic Noldor were the best possible weapon with which to keep Morgoth at bay, virtually besieged, and at any rate fully occupied, on the northern fringe of Middle-earth, without provoking him to a frenzy of nihilistic destruction. And in the meanwhile, Men, or the best elements in Mankind, shaking off his shadow, came into contact with a people who had actually seen and experienced the Blessed Realm.

In their association with the warring Eldar Men were raised to their fullest achievable stature, and by the two marriages the transference to them, or infusion into Mankind, of the noblest Elf-strain was accomplished, in readiness for the still distant, but inevitably approaching, days when the Elves would 'fade'.

As we can see, it was not a zero-sum game.

There's nothing like a Ban to get Man curious.
...
Calls on someone else to fix it.

What better alternatives do you see?

If it weren't for sending eagles and Gandalf, not sure what good Manwë has done.

He is called the "chief instrument of the second theme that Iluvatar had raised against the discord of Melkor", cf. Ainulindale. I certainly doubt it was a gratuitous title. He is the main organiser of the resistance against Melkor, he calls his brethren to the fight, he transmits Eru's will to the others (as the only one capable to directly appeal to Him). According to Osanwe-kenta, "Manwe was bound by the commands and injunctions of Eru, and would do this or abstain from that in accordance with them, always."