I have read that it is not uncommon for many men to find that as they age their body shape changes
The belly becomes more rounded -- even in men who are not overweight and who have normal muscle tone in their midsection I’ve heard it referred to as a return to a young boy's shape.
It becomes more comfortable to wear garments at either a lower or higher waist than in youth/mid-life.

A low waist can look just as unattractive as a high one.

I suppose that ideally an “in person” fitting by an expert would yield not only the best fit for waist, hips, and length but also for the length and fit above the waist.

With casual standard size kilts to me the fall to the top of the knee is everything. The waist is…wherever it is.
My task then is in belting the kilt in such a way that it neither rides up or down.
This may be a situation where a wide belt serves better than say a 1.75-inch belt.
Maybe why I favor "pirate" style 3-inch belts.