I think Kindle is becoming more popular for people who want to read books online. Magazines are declining in sales too, same with newspapers.
And frankly, I think DC and Marvel had problems before this pandemic:
https://www.forbes.com/sites/robsalk.../#31febea74d68
Really, Manga and original YA graphic novels have far less confusing continuity than superheroes comics, they have a defined middle and an end, I think the spawling universes of Marvel and DC have become a barrier to new kids picking up Marvel and DC. I think Marvel and DC spend too much time catering to their aging customer base over trying to get kids to pick up comics and kids enjoy these characters more in other media than they do in the comics.
Even without the pandemic, how long could Marvel and DC have sustained themselves on the same old readers?