Just my opinion, but the dependency on Chromium is a problem in itself. You don't need a full-blown browser to render HTML email. The fact that it is no more viable for a client to ignore HTML nowadays is something unfortunate, to say the least. Real people only need Emoji support at best (or at worst), because nowadays every from your bank to your local security expert tells you "don't click on links in emails", and your local privacy expert tells you to turn off every convenience feature related to HTML.

On another note, TFA talks about a "GNOME toxic development culture", which looks like a blanket statement. Does it really exist?