@bananapancakes
Shaw does not throttle the connection whatsoever. With YouTube, what may be happening is the route your device takes to a YouTube web cache may be heavily utilized in comparison to another route going to another YouTube web cache. Or the web cache itself is experiencing issues.
go onto community.shaw.ca to have someone looking It. There are engineer that are also present in there that can have a look into it. There was a time period where YouTube was broken similar to what you are experience for everyone east of Alberta. Shaw figured it out afterwards and resolved the issue.
Looks like there is an open thread about this.
https://community.shaw.ca/thread/35397