Your view is just a snobbish and rigid one, Sagan made science topics interesting for more people, from those people very likely many got inspired enough to pursue deeper science training.
Dumbing down is necessary to make it interesting for people who feel it's unapproachable, it breaks a barrier, I have no idea how you look at this and think "this is harming society"...
Carl Sagan significantly influenced Neil deGrasse Tyson (another popular science writer), for example. But I'm not sure if Tyson would have pursued science regardless of Sagan's influence.
Many physicists have written popular articles and books for the general population. Eg Einstein, Stephen Hawking, Brian Cox. Improving accessibility of advanced concepts is nothing to scoff at.
Even though I think you are wrong on this, you seem to be saying it like it's a bad thing ? Why ?
What, exactly, is wrong about inspiring high-schoolers ?
When explaining something to people outside of science, I was ok with 60% accuracy. Even 50% and some technical lies was fine if this would encourage them to learn more. Some came back to say "you lied!!" and these were one of my most cherished victories.
In lectures for 1st year students, I would have here and there an asterisk with "almost true", to which we would come back a semesters or two later.
Dumbing down science to dumb up people is wonderful.