I think some of the issue is the time between the original and the parody. How long ago was the original Space Jam? 1996! I bet you would be hard pressed to find it on DVD now much less anyone under the age of 20 to remember that movie aside from when their dad mentions it. Also-studios cranked out so many movies back then and there was a bigger amount of parodies. Naked Gun, Police Academy, Scream, anything Mel Brookes - now the studios are just about regurgitating old ideas (Fresh Prince, Jungle Cruise) or tacking on sequels (all the rest).
Although - I liked Jungle Cruise.