Second chambers are difficult to get right, and from what I’ve heard the Canadian Senate is one of the more difficult.
A second chamber which works well is a very useful system indeed - the old-style House of Lords was excellent at that - but unfortunately where a chamber is unelected it is too easy for folk to run around wailing “democratic legitimacy”. Yet when the chamber is elected it becomes difficult to give it lesser powers than the other chamber.
Where there is no established heretidary basis for the second chamber, I have a fondness for indirect election (such as used to be practiced for the U.S. Senate).
I would like to see a Senate that is elected but the senators for each province would be elected at the time of the Provincial general election. In the event of a vacancy, the by-election would be under Provincial control, not Federal control. That would make it regionally responsive as a counter balance to the rep-by-pop House which is heavily weighted in favour of Ontario and Quebec because of their large populations.