Yes, most people can't be natural born winners. That's how winning works, only a select few get to do it. Once too many start doing it, the bar raises and the numbers settle.

Everyone who exists is the product of an unending series of genetic winners. And things seemed to work just find before the 1960s. I regard having a decent life, marriage, kids as 'winning'. What happened?

So you either build a society that has balancing mechanics to keep losers in the game until they manage to become successful after an intial rocky start

Yeah, that, though I'd rather structure things in such a way that they don't start being losers at all.

Somehow I feel like you will still deflect blame despite being part of group 2.

You're mistaken, I can see the rottenness of society, and obviously it is the ultimate cause of mass shootings (as such mass shootings were comparatively rare in the past, if I'm not mistaken), but this does not absolve the mass shooters (not that you meant to absolve them).