Back in the 'good old days', before the cross-promotion antagonism that grew out of the MNW, talent seemed to flip between WWF/WCW fairly commonly (the traditional route was to get fired for drugs abuse), and I don't remember fans thinking much of it. Yet another wedge in society that people want to argue the toss over.
AEW and the current WWE appear to have vastly differing philosophies around how the business should be conducted. From a talent perspective, the opportunity to be a huge name (even one with appeal outside of wrestling) will be a huge draw to WWE for some, but they have to be willing to play it WWE's way - most will lose their name, gimmick, and any creative input into their careers. For some, this is probably a boon - they can go in the ring, but need a team of writers to shape their personalities. They also need to accept the frequency of WWE's talent culls and that they might be part of that.
Others will want the sort of career AEW can offer, and thrive in that situation.