I mean, sure, let's entertain the notion that it isn't okay. There's issues in many marriages that get to the point of considering divorce as a viable option, right? Incompatibility, infidelity, financial problems, domestic violence, substance abuse.. the list can go on. These issues can be fixed.
There's marriage counseling, couples' therapy, financial planners, rehabilitation centers, religion (for some).. that list goes on too, bc we have so many options available at the ready nowadays to help us fix these issues. So, there we have it, there shouldn't be any reason to not just tough it out and hope things work out for the best. "For better or worse", like it says in numerous wedding vows.
But that only works if both parties are willing to participate and actually have the resolve to save said marriage. Not everyone wants to do that, some people have different thresholds for how much of these problems they're willing to put up with, others would actually say that they don't have any problems. "Ah, come on, you know I'm kidding. Laugh a little" "It's just a drink, who cares" "It only happened once, I swear it'll never happen again"
People can learn a lot about a person through marriage, and sometimes, they might not like what they end up learning. Sometimes it's enough to wanna reconsider the marriage as a whole and reevaluate exactly what it is that they want in life. There's a point that can be reached where it can honestly become the best decision to have a divorce and just move on as much as possible.