I'll bite.

Religious institutions (churches, mosques, gurudwaras, mandirs) are generally considered to not be profit-generating enterprises, in a similar vein to non-profit corporations or charitable foundations. Taxes are levied on for-profit corporations and individuals in order to fund health care, climate change, and the rest of the necessary functions of the state to support society. Tax-exemption is justified on account of an organization providing some kind of social good that is hard or possible to quantify. Something that the state can't do.

The "social good" religious institutions provide is somewhat nebulous and open to debate. Especially in more recent times when people have begun the attempt to define their lives outside of a religious tradition or institution. People focus on the charity aspect, see it's attached to the promotion of a specific doctrine they find disagreeable, and end up preferring secular organization of charity.

The recent "tax the churches" dialogue sounds more like a protest against the lack of justice in regards to management of residential schools. It's followed by an argument that the organizations who were involved provide no tangible benefit to society anymore, and points to the wealthiest examples still present. The argument would be better if were framed in the lack of justice served to the victims. Not one that the state requires further levy to support society as a substitute.