Ah, thanks! I came across that a while ago but had forgotten about it. It seems to have come along quite a ways.
The main downside(from my perspective) is that it's a lot of moving parts, and I think I'd be more happy with just irc over tls since I at least know how that works :-)
Out of curiosity: what makes you say Matrix is over-engineered?
Video calls come thanks to WebRTC in browsers, Matrix is just a transport protocol. I think it's quite light.