They gave us a framework, one they knew wasn't perfect so they also included a way to change it but made it so changing it would be difficult so it couldn't be done a whim.
As for firearms they likely saw repeating arms becoming a thing as well as many other things, consider some of their ages when they put pen to paper.
My grandfather was born before commercial radio was a thing, when he died he'd seen us go land on the moon and have Dick Tracy's watch radio become reality in the form of smartwatches.
His father saw the birth of the automobile and airplane, electricity put to wide use, served in both world wars, saw man land on the moon, and all kinds of other innovations. Mother much the same except the world wars bit.
I've been around since before the CD, home computers, and the internet and look where we are now with all of that.
Foolish to think they wouldn't anticipate improvements in all walks of life, also several of them were abolitionists just not enough of them sadly.
That sex toy bit is untrue as well, as a blanket statement at least Franklin was a manwhore, but women were partners back then, there was tons of sexism and sexist laws and all that (not so) good stuff, really though who wasn't.
Like I said they left us a mechanism for change and if you can convince enough people that your position is the good one that change can happen.
Good luck given that there's only been 17 after the initial 10 needed to get the states signed on post revolution and one of those was there to cancel out the other (prohibition was a dumb idea)
I see that crimes against God thing there too, got bad news for you about a lot of the people involved in the major world faiths from when they were formed.
But hey, most of them have abandoned the majorly bad bits, don't stone children for cursing their parents anymore and such, slavery is strongly frowned upon by most of the 10 global religions with the most adherents.
Buck up buttercup, things get better, takes time is all.