Without the carepet and pad, I can tell the the bathroom and and bedroom
doors will have a large gap underneath.
Is there something made to fill this gap other than replacing all the doors?

Take the door off and screw a piece of wood to the bottom of the door,
then sand/plane flush. Paint door to hide the join. If the doors are
natural wood, use a brass or aluminium kick plate at the bottom of the
door.

If it's only a small gap them brush draught excluder might do well
enough.

Owain