We didn't see widespread expressions of dissatisfaction with Expedia until the lockdown phase of the pandemic when travel providers were simply refusing refunds and changing policies frequently.
There were multiple threads about Amex Travel/Expedia "nightmares" well before the pandemic. I personally contributed one of those stories following an absolutely terrible experience making an illness-driven change to a CX ticket that was completely bungled by Expedia and which Amex was unable either to explain or fix.
Having used Expedia a handful of times over the years (including showing up at HHV once and being told Expedia had not transmitted my reservation to them on a night they were sold out) I feel pretty comfortable saying that Expedia in general provides sub-par service and that I view Amex's increasing reliance on Expedia as a mistake if it wishes to maintain its image as a premium brand.