I could see some form of very valid criticism being levied against Disney's marketing strategies for sure. They overhype on basically everything coming out of the parks... even a new churro.
But continually holding everything to the standard of "WDI can do better" is a surefire path to disappointment. Of course WDI can do better. They could have built a full Marvel park if asked to. But that wasn't the scope of the project. Every project from the creation of Disneyland itself has been a compromise between blue sky ideas and the realities of completion.
Would anyone really be willing to argue that Disneyland was a huge disappointment at opening, because they had to wait 12 years for Pirates to open?
I think it is absolutely fair to look at what was presented and be disappointed in what we're seeing. To that end, saying "oh, they couldn't do a better job because they had to deal with a shrinking budget" is not a statement that deflects criticism but should lead to more, because you can compare what Disney is doing to what a Universal is doing, or even what Knotts is doing, and see that Disney is hurting themselves with those choices. Disney has been cutting their budgets, overpromising and underdelivering for a few years now, which is a huge problem and is going to cause people to react negatively.
Your last sentance here doesn't act like a good comparison like you might think. People on opening day would not be disappointed that PotC was not open because PotC was not even a concept, let alone an announced ride. The better comparison would be if opening day rolled around and Jungle Cruise, Mine Train, and half of Fantasyland were not ready to open, and would not be ready for half a year at the earliest.
If you tell your potential guests that you are going to build something, and show off early concept art, it is not unreasonable for those guests to then expect you to deliver on that promise instead of hemming and hawing and "oh, it might be in phase 2"ing things. You can't even blame the pandemic for this; Avengers Campus was slated to open last summer, and prior to the pandemic they had not started any construction on any potential E-ticket.
Also, stating that a thing is popular (especially in the opening week) does not imply that it is good. All it implies is that it is new and shiny and that Disney fans, who are preconditioned to come out and experience new and shiny things, are doing what they have always done. Pointing to Boarding Groups being grabbed up quickly during a time where the resort is at reduced capacity (and the land itself is limiting guests as well) also doesn't support this notion.
I think my main criticism of Avengers Campus as-is is that this is a prominent example of Disney willingly sacrificing the quality of their offerings in the name of saving money. The Marvel franchise has made over $29 billion and is one of the tentpole franchises for the company, and yet Disney decided to cut instead of spend. That's on them, and it is completely reasonable to be critical of that decision and the resulting land.
I get a place with tons of characters and shows plus the first new attraction at DLR in a decade that I can ride and enjoy that doesn't give me motion sickness. 