My biggest concern with acquiring someone like Eichel at this point is that the Ducks lack organizational depth at any position to deal from a position of strength. Let's assume that Buffalo would accept an offer I saw earlier in this thread: Rakell, Comtois, Perreault, and 2 1sts (21 and 22). So now you've got Eichel and Zegras up front and not much else besides Henrique and Terry. That's a worse situation for Eichel than he had in Buffalo!
And how do you improve the team going forward? You've traded your two best roster players in Rakell and Comtois. No one wants anything else on the roster except for Gibson, Lindholm, Manson, and Drysdale. Are you trading one or more of them as well? That's creating holes to fill holes. Free agency is expensive and most don't want to come to California. The prospect pool is average at best and won't return the type of talent needed to complement Zegras and Eichel now. You've traded your two best draft picks. Do you continue to trade future 1sts and 2nds to upgrade today's roster? Finally, Eichel becomes "the man" and all the pressure is on him. Zegras at 20 isn't ready to lead the team and none of the defensemen have the personality to do it. That's a lot of pressure for a guy that has no supporting cast. It all seems very risky to me with the probability of failure being very high.
Contrast that with LA's situation. They could trade from a position of strength (center prospects) to upgrade their center position without hurting the existing NHL roster. Vilardi, Turcotte, and a 1st for Eichel probably is close to what would be required. And presto, they upgrade from Vilardi to Eichel without losing anything off their remaining roster. Turcotte goes in the trade but Byfield is still there as a top center prospect. Eichel doesn't have to be "the man" because Kopitar and Doughty are still there. Makes tons more sense organizationally even if I think LA would be best suited to use their assets for other things.