Why this was not as big as Back to the Future?

One is a classic, one is almost obscure.
I know Innerspace very well, but I also know that if you ask around non film buffs, they don't. I loved it as a kid, but 30 years later it seems it's left out in the darkness.
They are very similar movies, but one is ingrained in our collective memory, the other is not.

My take is that Innerspace is aimed at a younger demographics than BTTF, or a less refined one. That's its mistake.
It pushes the adventure aspect of it too much, too far away from science and into fantasy: face transformations; dream sequences that are real; a one armed snap tool henchman; escapes that don't make sense; coincidences that are unbelievable.
There were too many "come on?!?" moments in it for smart kids that had nothing to do with miniaturization. It's like the writers wanted to add any "cool" sci fi idea possible to make it a rollercoaster ride. I think they went overboard and audiences rejected it.

For instance, the whole movie takes place in 24 hours, and for no good reason two improvised double agents are able to locate the chip and retrieve it from weapons traffickers that quickly...come on!?!