Bromelain is a protease.

If taken by mouth it will (in just the same way as any other protein) be broken into its constituent amino acids by digestive enzymes in the gut.

Bromelain is a very non-specific protease - it can cleave many proteins. Even in the (very unlikely) event that it can cross the gut wall intact and enter the bloodstream it would cleave any plasma protein (not just fibrinogen) that it encounters, with potentially adverse health effects.

Sometimes bromelain is used, applied topically, to treat burns - this is a sensible use of it.