Was Catch Me If You Can based on a complete lie?

No.😒
They changed a few things, but they primarily stuck to the true story.
Abignale was a consultant.

Yes.

It's become clear since 2021 that Abagnale lied about his lies. Lied about his exploits. Lied about everything.

Spielberg, Johnny Carson, and the rest of us have all been fooled.