Depends on your threat model. If you're worried about old people dying from COVID directly, then yes, it makes sense. If you're worried about the hospitals being overwhelmed and then people dying from car crashes and heart attacks, then targeted self-isolation of vulnerable people isn't going to help as much.

As a healthy 30-something, my chance of dying from COVID is about 1:3000, about 300x better than an 80-year-old. However, my chance of being hospitalized from COVID is about 3%, which is only about 7x better than the 80-year-old. The hospitals were overwhelmed, here (Bay Area) and in many other cities. Even now (2 months after the Christmas/January surge) Santa Clara County still has 21% of its ICU beds taken up by COVID patients.

U.S. life expectancy dropped by a full year during COVID. We were concerned about the 0.1 year declines in 2016-2018 from the opioid epidemic (which did affect young people), and this was 10x that. It'll be interesting to see how all-cause mortality has varied among different states in 2020-2021.