Barely worse than Teams or your typical web app. Needs polish for sure but the bar for web apps aren't exactly high.
Canvas usually breaks text selections etc. and accessibility. But what they do seem to perform much better than trying to get the DOM to do something it wasn't designed for.
MS Teams is among the worst pieces of software, that people have to deal with on a daily basis, because it gets shoved down their throat at their jobs. If something is even worse than that, even if "barely", then it is a complete disaster. A little "polish" will not be able to make it right.
When you delve into badly-performing web apps, DOM is almost never the actual performance bottleneck. It’s other things they’re doing. And in the rare cases where DOM is the bottleneck, it’s always that they were abusing it.
As for this case, I have never encountered a web app with performance (throughput and latency) problems like this. Not anywhere near it.
Similarly I don't think canvas is the bottleneck here.
Oh, and abuse is the name of the game. Almost exclusively the only thing the browser deals with is abuse. Logical consequence when the users are the one paying for it.
Canvas usually breaks text selections etc. and accessibility. But what they do seem to perform much better than trying to get the DOM to do something it wasn't designed for.