The decline in the US marriage rate is driven more by age at first marriage than by a rejection of the institution. While the percentage of people who will ever marry has only slightly decreased, the average time a person spends married in their lifetime is much lower because they are marrying later than ever before.
Contrary to the common belief that divorce rates are at an all-time high, they actually peaked around 1980 when roughly half of all marriages ended in divorce. Since that peak, the rate has been on a steady, multi-decade decline and is now considerably lower.
Sociological data refutes the argument that welfare drives non-marital births. Rates of non-marital childbearing rose most sharply in the 1970s and 80s when the real value of welfare payments was already declining. Furthermore, rates did not fall after the major 1996 welfare reform, undermining the theory.
The introduction of no-fault divorce laws was a legislative response to already-spiking divorce rates that were overwhelming the court system, rather than the cause of the increase. Data from states like California shows divorce rates were already rising before the law was changed and simply continued on the same trajectory afterward.