Thing is Slott did write him as serious in Amazing Spider-Man at times, such as here from #680 (albeit co-written with Christopher Yost).
Johnny's not serious all the time, but knows when to step up.
FF Annual #32. They did date, but Psycho-Woman, the daughter of Psycho-Man, had the woman artificially inseminated with Johnny's sperm instead of it being a roll in the hay. In the end she jumped into the FF time platform and disappeared into the time stream carrying Johnny's unborn child. If anyone at Marvel still remembers that and does a follow-up it would be major surprise for me.
https://www.comixology.com/Fantastic...l-comic/621944