I'm not saying that there isn't any interconnectedness for DC. But I think there is a definite difference in degree between DC and Marvel here. How large it is, I don't know, but I've read plenty stories of DC writers lamenting the hassle of getting the use of other characters for cameos or guest-starring.
And no, I didn't forget Justice League. I omitted it because I view a difference of degree for Wonder Woman's importance in that title compared to her role in Justice League Dark, and because I don't regularly follow it and thus couldn't say anything about how JL-JLD-WW tied to each other.
Is there a way to quantify this? One way is to look at cameos and appearances in other books (numbers via the marvel/DC fandom wikis). On one side I take Harley Quinn, on the other Kamala Khan (Ms Marvel). Both are relatively new characters and have seen considerable push from their respective publishers. They also have somewhat similar number of total apperances.
Total apperances for Harley during New 52/Rebirth was 383. Of these 140 was in her own titles (her name in the title), 135 in team books as a member and crossovers (Suicide Squad, Heroes in Crisis), and 108 in other titles. So Harley Quinn's appearances is roughly one-third own books, one-third team books as a member, and one-third in other titles, with a slant towards the first two.
Kamala Kham looks noticably different.
Total apperances since her start was 307. Of these 48 was in her own titles (her name in the title), 89 in teams books and crossovers (Secret Warriors, Champions, Marvel Team-up, and various Avengers), and 170 in other titles. So her appearances is one-sixth in her own book, one-third in team books, and more than half in other titles.
While not conclusive, I do think it is quite illustrative.