I've C& R a few muskies and lots of big pike. I've never used a cradle for them, but could see how it would help. The thing with pike & muskies is that they have relatively narrow boney mouths and lots of spikey teeth. The last thing you want is for that fish to go bezerk and start flopping when you've got your had anywhere near its mouth. The cradle minimizes flopping and makes it easier to get leverage on the hook.

I don't know about cradles for steelhead or salmon, they have no significant teeth and much softer mouths. With a single barbless hook this should not really be necessary. If you aren't fishing single barbless, you shouldn't be releasing fish.

I think if you just feed the fish a bunch of slack and wait 30 seconds, they'll unhook themsleves with a single barbless about 25% of the time. Otherwise, it is rather straighforward to just back the hook out by hand or with a pair of pliers while the fish is still in the water.