Long-time Red Queen opinion that might get me this reaction, and it's a long rant.
I have a hard time liking Thomaven, not because of them as a couple, but because Aveyard gives us so little information about Thomas, even though he has such a huge impact on Maven's character. Some might say it's intentional writing that adds mystery and tragedy, but I see it otherwise.
Let's start with the positives:
I highly appreciate Aveyard for not making Maven's bisexuality merely a decoration or a shallow representation. Other popular series would often label their characters bisexual and have them recall their past relationship once in the whole multi-installment series and be done with it. *cough* SJM *cough*.
The implication of his romantic relationship with Thomas was set as early as Book 1 when he talked about Thomas with such grief and reverence during the secret Scarlet Guard meeting. This was followed by a confirmation from Maven himself in King's Cage during the breakfast scene.
Every time Thomas was brought up in conversation or in his private thoughts, it would inflict deep sadness and even momentary sharp pains on Maven. The thought of Thomas, the boy he loved and who loved him, and Thomas' violent death, consumed and haunted him.
And when Maven's final POV in Broken Throne reveals, in his time of deep distress and humiliating defeat, that Maven took comfort in the thought of him dying, hoping he'd see Thomas once again.
The way Maven changed completely after meeting and losing Thomas piqued my curiosity as to what Thomas, as an individual, was like. Who was this Red servant that captured a Silver Prince's heart?
That's why Broken Throne disappointed me as a Red Queen fan, and my frustration with Aveyard's way of writing the series and her characters in the latter half of the story was more prominent.
Not only did Thomas remained shrounded in mystery. Even in Maven's final POV when he declared to the reader that his love for Thomas cuts him deeper than Mare.
Thomas was the only person in Maven's short life whom Elara never tainted. Only when he died did Maven beg Elara to erase the memories and the pain of losing him. During his betrothal to Mare, Elara was around and prevented Maven from loving Mare as strongly as he could have. Since Mare was not just a Red, but also a Newblood and a political threat, Elara did not want another "Thomas" or Maven pulling a "BUT MOTHER I LOVE HER." Too bothersome. It would risk everything Elara sacrificed Maven and so many others for.
I genuinely was expecting more Thomas lore: what he looked like, what he sounded like, what his surname is, and whether Maven ever wanted to have his surname. What activities did they bond over, or at the very least, what words or phrases did Thomas love to use? But Aveyard gave us nothing. None.
I might be nitpicking or overly demanding, but keep in mind Broken Throne also concluded Mare and Cal's relationship and future children, and loads of heartwarming interactions between Evangeline and Elane being a couple without the fear of war and suffocating expectations of Evangeline's parents.
Heck, Aveyard even dedicated a whole segment to a new set of characters, sharing their outside perspective on the main storyline. Aveyard gave them names, backstories, occupations, physical descriptions, and a thrilling boat chase; even the servants who tended to Mare during her imprisonment had their moment.
Four books, two novellas. One of which centered on Coriane Jacos, a character long gone before the main story began, who, like Thomas, haunts the narrative and those who loved her, such as Tiberias, Julian, Sara, and her son, Cal. Yet Thomas still remained a name whose existence was only known by Maven, and even he is gone.