I think he has some points but some things are missing here. First is, what is the purpose of marriage? Removing religious reasons, marriage is an institution of finance and legality. There are some financial benefits, such as taxes (claiming marriage with better tax benefits) and legality that comes into play when it comes to benefits (health insurance, life insurance, etc). The risk with marriage on the financial aspect is, your handing someone a loaded gun to ruin you (or both) financially. I've had this conversation with my wife (we are both millenials, we also had out first kid at 21 and 20, so for our generation, we are outside the norm), if we didn't have kids, we may have never gotten married. Which is , marriage makes the legal aspects and financial aspects of having kids easier. The second point is, the older gen-Z are 26 years old. I think its not too surprising many of them are not settling down. Many are still to young to start settling down, especially given a trend over the past few generations where people are putting off starting families older and older and waiting to be more financially stable. If your not gonna seriously start having kids until your well into your 30s, why get married in your early to mid twenties?
Addition: I will give it to the guy on Gen-z being affected by witnessing toxic marriages. What I will say is, with that taken into account, lets not count out Gen-Z on marriage dying. Maybe this will be a generational lesson in rushing to marriage. Gen-Z will put off marriage, but have more stable and fulfilling marriages.
But more importantly, with a quick google search, the Gen-Z age range is 11-26. Half of the generation are still children and teenagers.