I know what you mean Melvil, I think it's partly dependent on the adult - if you are the sort who is happy to act like a kid a bit, I expect you get plenty out of it. But it's annoying if things are over simplified, or dumbed down. It ought to be possible, with a little thought, to make exhibits both interesting and challenging to adults, and fun for kids. But I think too many people aren't prepared to read an information card, either for themselves, or to the kids, so they just wander round in a daze staring at things, while the kids press the buttons and stuff, without really knowing why.
In fact I've often thought of opening a visitor centre type attraction. There would be loads of buttons and lever and things, that lit up lights or sounded buzzers or whatever. They wouldn't actually MEAN anything or teach anything, but that's ok, it would be 'interactive', and that seems to be the important thing.... In fact only about half of them would have to work at any one time, the kids still smack the hell out of them anyway. As long as it had a big car park, and a themed burger bar, the great British public would flock in...