YYZ is a pretty profitable route for many carriers. They wouldn't fly there if it wasn't.
Knowing the demographics of the GTA, I would say that EY are not lying when they say in their press release:
“We are thrilled to announce more flights to cosmopolitan Toronto, one of the most successful and popular destinations on our global route network,” said Robin Kamark, Etihad Aviation Group Chief Commercial Officer. “This news has been eagerly anticipated.”
https://www.arabianbusiness.com/transport/401785-etihad-to-increase-number-of-flights-to-toronto
Etihad have a few problems to deal with due to unwise investments they made in other airlines, but their core business of flying is strong. There are a few of the usual suspects on here who try to cast doubt on any positive news about YYZ, but the facts are clear: Pearson is Canada's largest airport and biggest international gateway, and there are reasons for this.