There are many reasons why we should not compare our spouse with others.
The first being that it will hurt the relationship. If a person starts comparing partners and then one of them feels less valuable, the comparison has just been a failure for both people. When we compare our partner to someone else, it can lead to resentment and a feeling of superiority or inferiority.
Secondly, it is unfair to compare other people’s relationships to your own when you are not in their marriage. The reason is that there are no two people who are perfect together. Every relationship is different. You don’t know what challenges they might be going through or what they see as challenges in their relationship.
Lastly, if you want your marriage to be better than this person’s marriage, you need to make it happen and stop looking at other people’s lives and relationships as something they can measure up against their own.