The failure of the Arrowverse keeping its promise of bigger and grander crossovers.
The Arrowverse crossover era began when The Flash’s Barry Allen paid visits to both Arrow and Supergirl. Each successive crossover grew in grandeur and storytelling, bringing iconic DC stories to life. The "Invasion" crossover could be considered as Supergirl's official welcome to the Arrowverse. Subsequent crossovers such as "Elseworlds" and "Crisis on Earth X", involved more ancillary characters from all the shows while telling broad, engaging stories.
Crisis on Infinite Earths crossover teased even grander Arrowverse crossovers. The final moments of Crisis set up what many believed to be the Superman & Lois was later scrapped, likely due to COVID protocols - effectively neutering the collaborative aspect of the franchise the Crisis had so painstakingly developed.
The Arrowverse post-Crisis has had to take a step back and regroup, rethink how to best approach the multi-show events that fans look forward to. Currently, Superman & Lois isn't even acknowledging the other shows or the Arrowverse, although The Flash name-dropped Superman in its recent return. Batwoman’s acknowledgment of the Arrowverse so far consists of one Supergirl mention in its season 2 premiere.
In the long run, having to break their promise of more crossover integration may benefit Arrowverse shows. No massive crossovers mean no schedule juggling and production delays in the show’s individual seasons. Planning large-scale crossovers have been reported to be logistical nightmares. Without the crossovers, Arrowverse shows don’t spend space and time setting up crossovers; this limited focus allows them to become more self-contained, making for tighter storytelling.
While scaling back the big crossover events may be disappointing in the short term, that does not mean the Arrowverse is abandoning the crossover concept. They have taken a new approach to keep Arrowverse shows connected, that being of the single character crossover. Although nothing has been announced by producers it would be hard to imagine Supergirl coming to an end without at least one more adventure with her superhero BFF, Barry Allen. The Flash's Jay Garrick just completed filming a return of Arrow’s John Diggle who will visit multiple shows this year, fueling speculation that he may be laying the foundation for a CW Green Lantern. Even without crossovers, the Arrowverse is bigger than ever.