Pepys attitudes and behaviours in that regard were unremarkable for a man of his time and class. It would have been more surprising - and more worth commenting on - if he’d anachronistically endorsed modern standards of sexual propriety.
It's an absolutely fascinating read, and it's well worth reading, but you should not fall into the trap of thinking "well, that's just how it was back then"; Pepys was abnormally badly behaved on a number of axes even for the time.
And then, go back to the original point for a bonus, and consider what you know about the general behaviour and attitudes are of the people in England 400 years ago.
> And then say that tell me you know that 'casual sex' is the general behaviour and attitude of everyone.
I said it's normal.
> what you know about the general behaviour and attitudes are of the people in England 400 years ago.
Plenty. Pepys wasn't that weird.