It's "a reason", yes. Legit or not is only for the two people in the marriage to decide.
This is the exact reason I started waking up. The WTS says "no", emphatically. Divorce is permitted only if fornication is committed. They allow three reasons for separation: willful non-support, extreme physical abuse and absolute spiritual endangerment. After my research, I found those three reasons completely bogus and without scriptural backing. Here's the bottom line, scripturally:
Matt 19:9: "I say to YOU that whoever divorces his wife, except on the ground of fornication, and marries another commits adultery." Note the emphasis. The adultery is committed only if another marriage ensues if the divorce is for any reason other than fornication.
Paul knew that happy marriages were not always possible. Thus, 1 Cor 7:10, 11: "To the married people I give instructions, yet not I but the Lord, that a wife should not depart from her husband; 11 but if she should actually depart, let her remain unmarried or else make up again with her husband; and a husband should not leave his wife."
The WTS attibutes 1 Cor 7:10,11 to separation. There's really no distinction here. Either way, it's a departing whether you call it separation or divorce. The sin comes in when, post-departing, one of the spouses has relations with someone else.
I can tell you unequivocally that I am super unhappy with my marriage (over 20 years). My spouse has given up. I have given up. It's only a matter of time before we part ways. For me, living alone would be better than being in a miserable relationship. We don't fight anymore. We rarely even talk. Not a good way to live. It's a lot harder to part when the religion has such a major role in life.