It is absolutely ridiculous to say say that it’s engaging in zenus if you don’t get along with your spouse. I am estimating that at least 20%, and likely more, of frum marriages, are with spouses who do not/or lose respect or liking to one another. Not only in this generation are there such marriages, but in all generations were there such marriages. With marriages that were completely arranged, I would not be surprised if the unhappy marriages were closer to 40%.
I say kol hakovod to those who MUTUALLY decide to continue to be married despite really wanting to divorce. To say such that people in such marriages engage in znus is not only ridiculous, but it’s a disgusting thing to say.