While it gave (young) women and a small percentage of men the ability to sleep around willy nilly without commitment I firmly believe that the overall result of the sexual revolution has been so negative its long term badness lies somewhere between the Taiping rebellion and the burning of the Library of Alexandria.

Previously society was at an equilibrium that as an average man you would find yourself an average wife who was (ideally) dedicated to you and you would support each other in your journey through this mortal coil. That we were in this situation was not an accident but the result of thousands of years of cultural evolution. It wasn't because some council of patriarchal elders decided to enforce traditional norms but because societies with traditional norms were better fits for human civilization so they outcompeted other ones until the alternatives were wiped out and trad norms became dominant (and no your two examples of current matriarchal societies are not a counterexample, look at their size and influence versus ours, if we wanted to we could remove any traces of their existence in less than a few months).

However with the sexual revolution this contract has been destroyed and we are in a state of free for all. The consequences have been dire, from Japan's unproductive herbivore men to the pandemic of single mothers in the west, especially among lower class people.

While loose sexual norms might work well for the sort of upper class elites who have safety nets to fall back on (and are the main people pushing this stuff) they wreak absolute havoc on the working class who don't have this support. Yes the Yale graduate who slept around will still be able to find a high quality husband to stick with her due to her class and connections but the community college woman risks being pumped and dumped into a single mom despite the fact that there are an order of magnitude more of the latter than the former. What's worse is that the Yale graduate will continue to support sleeping around saying that it did her no harm and ignore the destruction of the social contract and damage it does to people less fortunate than her (ironically she probably identifies as an intersectional feminist...).

Indeed there was research recently showing that while back in the day both rich and poor kids were roughly 95% likely to live in a two parent family at the moment although the rich still have a 85% two family rate the amount of poor kids in the same situation has dropped to 30%.

The sexual revolution has given men the freedom to not commit, while 100 years ago if you got a woman pregnant both social norms and her family would oblige you (forcefully if needed) to marry her and provide. Now as a man you are free to abscond your duty to your own child. Once again it is not the UMC doing this because they are better able to plan pregnancy and better abilities to handle unexpected ones but poorer people who don't enjoy any of this luxury. This is so extreme that among older working class women "Where are all the good men?" is now becoming "Where are all the men?"

This is before we have even gotten to the point of the damage the sexual revolution and our sex obsessed media which exaggerates everything further to maximize clicks has done on average and below average males. Your average man sees Chad on the TV screen effortlessly getting women to spread their legs (sometimes with a scene in which Chad meets a new woman which immediately cuts to one in which she is in his bed) and starts to believe that this is what life is like for the top 20% even though this is total media fiction (compare to how people overestimate the percentage of minorities in the country; minorities are overrepresented in the media, again due to our Yale Graduate believing this helps corrects for some past discrimination, then normal people see this increased amount and believe this reflects the real world).

Thus these average men get disillusioned with women and society (some even turning to in*cl movements), believing that all women get into bed with Chad two seconds after meeting him - because it is what they see on TV, and TV has become the main way most of us get information about the state of the world. Due to this these men are much less invested in their community - having a family meant that you wanted society in general to thrive because it meant your family would also be better off and it discouraged you from acting like a loose cannon because then your family would suffer e.g. the dad of two kids is much less likely to go on a shooting spree. Your slightly below average modern man does not have this moderating influence upon him anymore.

Thus in exchange for about half the population being able to sleep around no strings attached for a few years we have irreparably damaged the bonds holding society together. This damage to the social contract is likely irreparable. In the best case we may be able to adapt to this being the new normal while spending more and more resources on ersatz remedies to mitigate the negative effects. In the worst case western culture may just be in for a real time demonstration of why cultures with loose sexual norms did not survive long.

TLDR: Title.