There doesn't seem to be much evidence to suggest Delta produces all that much more severe disease.[1] The CDC says "it might be". Much more infectious, yes, but not more deadlier or at least not so much deadlier as to explain the Alberta numbers (especially comparing a population that is 70% vaccinated now versus 5% in the last wave).

And again, we aren't seeing the same impact outside of Alberta. In the US, which has a lower overall vaccination rate, the death rate is actually lower than prior waves.

[1]https://www.cdc.gov/coronavirus/2019-ncov/variants/delta-var...