Old lenses are generally fine when stopped down to sensible apertures in my experience. What’s new is the expectation that lenses should be ultra sharp wide open. Expensive lenses are a very niche enthusiast market now, so the design criteria aren’t especially rational.

An exception would be old kit zooms from the film era, which really are awful, since they were designed for people who rarely even went up to 8x10 prints. Modern kit zooms are usually very sharp lenses, though.