Completion is the length limit
If your 15 second Reels get finished and your 90 second ones die in the middle, you are not "too short for the algorithm." You are long where you get boring. Teach or tell the story, then stop.
A slightly longer Reel is worth trying when you have a series people already watch, or when the idea is a list they want to finish. Check average watch time in insights, not a template from a different niche.