Historically, it was considered 'unwise' to use exits on the same side as an engine fire to evacuate. e.g."Evacuate starboard side only" PA.
Since the Airtours B737 disaster at Manchester Airport, when such a PA was made by the Cpt, the philosophy remains, but in theory only. In the Manchester disaster ALL the main exits on the starboard side were affected by fire (AFT right) or jammed (FWD right) leaving the pax controlled right overwing exit as the only means of escape!
The FWD left door was eventually used and 17 pax escaped using this door, which was 'on the same side as the fire.'
On larger aircraft, the distance between FWD and AFT most doors and the engines is quite considerable. C/C should therefore be taught to assess the usability of each exit, regardless of which side of the aircraft the fire is on, before using it.
The Captain may still nominate exits, based on information from ATC or emergency services, but, as proved in Manchester, usable exits on the other side should not be discounted.