There weren't separate categories for "discouraged workers", "underemployed / irregularly employed" workers, etc. in previous recessions. The current U-6 number becomes more comparable to previous "headline" numbers the further back you go.
Comparing current "headline" numbers (U-3) with old headline numbers (when there was just The Number) is kinda like comparing current automobile death rates with those of the early 1960's. Yes they're lower but there are the matters of airbags, ABS, seat belts, unibody construction, etc.
If you want to be that way, go back to the early 60s when welfare wasn’t included as employed.
The current rate would probably be near 20%.