You're getting some of the best rates possible here in Canada at that point. You may be able to grab a little extra yield (around 0.25%) off of a money mark fund like ZMMK. However, you would be giving up some liquidity in that regard as you'd have to buy in and out of the ETF when needed.
Obviously on that large of a balance it isn't negligible money, about $625 a year. You just have to factor in the convenience of being able to withdraw from something like Wealthsimple cash near instantly whereas with a fund like ZMMK it may need a day or two to settle and then a day or two for the money to hit your bank account. Unless you broker with WS Trade. Then I believe the process would be faster.
The higher rates are now in the United States. But that brings on a whole other list of issues for someone who wants to keep currencies constant plus avoid FX swings.