I thought it was being done for web apps like Google Docs now, and I thought one of Microsoft's cross-platform toolkits used <canvas> too (though I don't think this toolkit itself will see broad adoption).

There's an active proposal for rendering html in canvas to control styling. Text rendering and accessibility are main focuses for the proposal.

https://github.com/WICG/html-in-canvas

It already happened. WASM. And it's generally been used well.