At about minute 34:45 in this speech…
…Kevin Spacey makes a very good point: Many people complain about their audience’s shrinking attention span, and yet people still find 12 hours to binge-watch a TV show.
So instead of trying to trim things until you can meet an impossibly short standard, think of it this way:
There’s a lot of crap out there, and people are really good at sorting through it quickly. Attention spans are not shrinking, not at all. In fact, people have almost unlimited attention spans for things that are important to them.
If your audience is looking at their phones, the problem is probably not their attention spans. The problem is probably that you didn’t find out what was important to them before you opened your mouth.