You are correct active defense is the only workable defense.
Patton “Fixed fortifications are monuments to man’s stupidity.” it was not completely true but a good working view for the most part.
The Maginot line was a success in that defended the section of border that it was supposed to, it was a failure in that the people of France thought it protected all of France.
Agree. The conventional wisdom is that they don’t work. When fortifications are breached, usually there is a failure in some other aspect—planning, guarding, strategy, construction. Not the walls themselves, but the reliance on the walls and failure to do other things.