NTT is 90% of the reason, yeah. Plus one of my first mainstream WW comic was by Byrne and she was part of the 'Wonder Family' with Diana, Hippolyta, Artemis, Cassie and Helena so I always saw her as part of the family even if DC and some fans don't.
Most of the Amazons and Amazon adjacent characters are mythical archetypes. Donna belongs to both the Amazon world and Man's World.
Donna has human struggles from having to search for her biological family to being a 'Team Mom' for the Titans. She's like the older sibling who has to parent the younger siblings but whose struggles are often overlooked. What makes it even deeper is that despite putting other people first, she is not always as stable as she likes to be, she is someone who can and has cracked under pressure and made mistakes. That makes her more human and relatable.
In a weird kind of way, the fact that even DC/WB ignores her, the WW comics often forgetting her existence and the fact that she's getting passed over in favor of Cassie and Yara and the other Titans having gotten more exposure in other media while she continues to be on the sidelines, has only endeared her more to me. Even on a meta level, she's the older sibling who does the most but never gets the toast.