Schofield stepped down as host in May after he admitted to an “unwise but not illegal” relationship with a staff member over 20 years his junior behind the scenes at This Morning.
Last month, the 61-year-old's long-time co-host, Willoughby, 42, also announced she would be leaving.
This followed security officer Gavin Plumb being arrested over allegations he was plotting to kidnap and murder her.
Finnigan had hosted This Morning with husband Richard Madeley for 13 years from 1988 until 2001, before they went on to host their own show on Channel 4.
She told Saga magazine on a new chat: "I no longer watch it, and won’t appear on there to talk about my book.
"This isn’t a protest, it’s just a very different show than it was when we were doing it.
"I know the politics inside television are extremely dense but it seems to me to be an extraordinary disaster of a stage in This Morning’s life that I don’t think needed to happen.
She said of Schofield: "Phillip is not a close friend but he is a friend and I must admit I simply cannot understand why he had to go..."
Willoughby's departure followed a difficult time on the breakfast show, culminating in her kidnap plot. She confessed that This Morning "wasn't the same" after Schofield left.
On October 10, she said in a statement that she would be leaving her coveted position after 14 years and that it had been an "honour to just be part of its story" but made the decision for herself and her family.
Finnigan's statements follow her husband Madeley describing Willoughby's decision to leave as a "a very brave, wise and courageous thing", during a chat on Good Morning Britain.
Former This Morning host Eammon Holmes has also slammed the show as toxic.