At the risk of being repetitious, and it was covered a short while ago in another thread, the only part of the so-called "airport tax" that is a tax is the Goverment's APD, well-described above.
The rest is simply the airport's charges to the airline related to passenger traffic; ie the more passengers the more the airline pays, plus any other charges the airline cares to add.
The airlines started calling these charges "airport taxes" and adding them to the price about 15-20 years ago, so as to be able to appear to charge the same fares but get more revenue, and they blamed the airports for "adding" these charges, whcih had been charged, in fact, since the 1950's.
Then the low-costs started separating out other costs they incur in running an air transport business and charging them separately under the totally false name of "airport taxes".
Among the most blatant additional charges are
Booking Fees
Credit Card Fees
Wheelchair Fees
Baggage Fees,
Early Boarding Fees
etc etc etc.
This is what creates the excessive charges, which should, of course simply be quoted and charged as part of the ticket price, as used to happen until the "airport tax" trick became so popular.