Where do Uber, Lyft and taxis pick up at Miami International Airport?

Miami International says taxi and ride-app pickup zones are on the arrivals (ground) level, outside the baggage claim areas (Miami-Dade Aviation Department, n.d.). Its FAQ lists taxi service as the on-demand option and describes bus and limousine service as pre-arranged.

Taxis there run on the meter, and the airport's rate sheet lists no flat fares; the published rates and what they add up to are on the Miami airport taxi fares page.

A pre-arranged car is the one that does not need you to find any of that. Give the desk your flight number, the pickup is tracked from the aircraft, and the captain meets you inside the terminal, so you are not choosing between a taxi line and a ride-app zone with luggage.