As another commenter noted, this will not reduce senior's income in retirement, but in their working years, and the contributions will be tax deductible so ~20% less than what they spend, along with increased benefits paid by their employers.

And also, as someone sort of pointed out, a change to the GIS clawback makes this go away entirely.

This is a pragmatic move to ensure that Canadians are not solely financing other Canadians retirements.