I'm only speaking as a New York theatregoer, that travels out of country for NY for shows. I will say since the reopening of Broadway there have been a number of factors that have deterred regular "Theatre tourists" to the city.
1) Costs have become prohibitive: on the same dollar budget from 15 years ago where visits would have been able to see 10-12 shows, now they can only afford to see about 3-4. As well, costs for accommodations and to visit have increased so much that it has left many international travellers choosing cheaper destinations (within country, or places like Poland, Eastern Europe, tropics).
2) Safety within the city: as a visitor I have seen the exponential increase of crime and safety concerns especially in the last 3 years: drugs, thefts, holdups, violence, mugging, drug use, the "dirtiness" of the city and its streets has left many choosing other destination
3) While some will say that for Canadians its a "political" protest, I will say that much of it for Canadians lies on their own cost of living - many can no longer afford any luxuries and have used the politics as a scapegoat, but for many cost of living compounded over three years has had many giving up their holidays or entertainment in order to make their house payments or pay for food along with their weakened dollar. Many are finding that a single subscription service becomes their form on in home entertainment that eliminates the other expenses for date night (parking, dinner)
4) Lack of interest in productions: when considering that many who are regular theatregoers used to spend on 10-12 shows and now only see 25% of that many have expressed they want what they see to be "the best". while sometimes that is spectacle or a celebrity, many have expressed that they have grown tired of seeing politically motivated shows, heavily focused on race, political messaging, lecturing. They also no longer truly are moved by "celebrity" (this is not to say that George Clooney isn't going to sell tickets) but there really isn't the strong draw as there used to be (and yes, people will list stars who have come in and brought the money, but it also costs money to bring them).
While I feel that we are in the midst of a early 90's slump, I hope that producers would take this time to reevaluate. I've compiled my own points over the last season in my discussions with others and believe that in order to revive the template: They will need Hollywood or recording stars to recognize that they can't take the same paycheques they need to look at this as a place to hone their craft and skill (similar to West End and British actors, who take on a 2-3 month play between films, every 4-5 years, To attract younger audiences and rebuild they need to remove lecture styles and political messaging (no 25-30 year old is going on a 500$ date to be lectured ), We have to use imaginative stagecraft and replace the "hydraulics" and lifts and automation and go back to old techniques to transform the stage, lean out the administration and assistants (in many companies there so much bureaucracy. And probably my least favourite, and most painful of them all is musicians will have to go down yet again to 7-9 unless supplemented with actors.
Tours would hopefully tour with the "straight from Broadway" casts that occurred in the 60-70s to amp up the excitement. and lastly I believe the new works need more time in development before they are shared publicly, and not deliver half baked works.
Anyway these are my conclusion after a pretty intense 10 months of my own discussions, investigations, and experiences.