That's like saying those young adult paperback novels aimed at teens like Gossip Girl have substance. They don't. Just because the songs I mentioned aren't as empty as dance songs don't make them any less pop fluff.
Anyway dance music is still popular so I guess they're going that route. And Jennifer was never a trendsetter. First album was Darkchild R&B/pop, which was popular back then, and second album still had that type of sound, but when it was failing, she jumped on the urban bandwagon. She stayed with that sound for TIMT, then Ryan Tedder was popular in the late 2000s so she used that for Rebirth and RedOne for Love.
Having substance means singing something important that people care about. Love is practical topic that has substance because it's a universal theme which people care about. So yes even though though those songs weren't revolutionizing material they pertained to a subject which is more important than partying and dancing the night away, so they do have substance.
Well, maybe she will have a TTAL era
Live It Up will be like Blow Me, very typical predictable song => still success but has no impact
2nd single will be like Try - a sleeper hit
And then when everyone thinks she's over, she will have her JGMAR - in this case an urban single that goes to #1
I'm not talking about some Ray of Light type album. Those three songs you mentioned have substance.
Her last several singles are about getting "on the floor", "dancing again", "goin' in" and now, "living it up". That is not substance.
If that's the argument you're making, Dance Again is not about partying and having a good time. Read the lyrics. It's on the same level with the other ones you said have substance.
You also didn't listen I'm Into You, and even Papi.