Ooh, Grandma Engine sounds good... FWIW, when I tried to make flickscreens from scratch, I sorta pulled it off after a day or so of tweaking, but I had the problem where if you were holding down left when you crossed the screen, you'd need to press left again to get the player character moving again. For some reason I couldn't see a way to solve that issue, and it was totally breaking immersion for me.
I'm honestly quite suprised something for making generic platform games hasn't cropped up over the recent years, given that platformers are sort of enjoying a rennaiscan.... a comeback. I bought something called Platform Studio about 5 years ago, which was OK, but it just felt very lacking in soul, and the jump action was horribly stiff and couldn't really be tweaked to life.
I'm still of the belief that the perfect 2D platformer hasn't been made, and that the genre has a lot of exciting places to go, especially given the ease with which modern computers can juggle 2D environments, physics, etc...