There are things to criticize about Jacksonville International Airport (like no international flights) - but I don't think I've ever paid attention to the ceiling heights. As for the length of the walks - never paid attention to those either. My 90 year father - who uses a walker - does just fine. For people with mobility problems - it is very easy to get a porter with a wheelchair.
How long did it take you to get through security? We've never waited more than about 10 minutes (OTOH - we don't travel the day before Thanksgiving).
One thing I like about the airport is the easy parking situation. About $4-5 a day for off-premises lots with shuttle buses. In fact - before 9/11 - there was a free 45 minute lot right next to the terminal where you could park while you picked up your arriving passengers. Also - the airport usually isn't very crowded. Easy in and out when you're dropping people off or picking them up. Curbside checking is also easy.
Are the food offerings limited? Yes. About what you'd expect in a smaller airport with no connecting flights. There's usually not much reason to hang around the airport whether you're coming or going. OTOH - there are good hotdogs and bagels (and the normal junk food places) if you simply have to eat something.
Note that I usually don't fly AA - but I have a flight on AA in July. I'll make a point of looking at the ceilings

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BTW - I never knew what the quick reply box did either. Robyn (near Jacksonville)