For a day trip to LA? I usually arrive 60-90 minutes before my flight.

Even that is overkill. With TSA Pre/Clear and no checked bags you can easily roll in ~45 mins before the flight.

I have Precheck and typically clear security in under 10 minutes. That said, 45 mins is cutting it close for me. Typically I arrive an hour before so that I have a buffer against uncertainty (Precheck lines can be surprising long sometimes).

Most people who travel a lot like that are probably pre-check, maybe even clear. I am, and usually I get to the airport roughly when boarding starts if I'm flying economy (assuming boarding starts with first class). It's certainly not 6 hours total in the airport.

This said, I'd really like better trains since flying sucks still. Planes are dirty, expensive, and airports are quite awful.