Are you talking about racing downhill on hardtail? You won't be competitive but it's not impossible to ride down a hill on a hardtail.

Dudes used to race downhill on hardtails. Some of them were lucky enough to have suspension forks too! Seems a lot of those Euros wound up hucking their bikes in the woods, though.

Ooh, I did see at least one full-squish in first video (an olde Offroad) and at least one in the second (an olde Trek)