The history of model aviation is fairly lengthy.

R/C models were flown at least as early as 1934. The first were just single channel rudder control to try (hopefully... it wasn't reliable) to get the converted "free Fight" model to stay in visual range. By 1936, 2 and 3 channel radios were starting to be used.... but the way they operated was still very crude. The technology revolution of the 1960s created by development of the transistor, quickly followed by the IC chip is what finally allowed reasonably light multi-function R/C systems.

The current transmitter designs are still based on technologies developed in the 1970's. The addition of the Computer control mixing was developed in the 1980's... but the main radio frequency boards were not changed... just the section between the stick and the RF board suddenly included a small computer.
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On the ailerons... it sounds like the servo is not recentering tothe same point each cycle. This could be the servo having a problem with age.. or it may be just an overly sensitive control setup. If you are using a PPM based system, you might cur it wth going to a PCM system, as the transmitter sends out a more precise servo position signal, and the reciever sends the servo to a more precise position.

Digital servos plus PCM = extreme precision in repeatable control centering.