Foot orthotics or supports are supposed to improve biomechanical abnormalities of the foot and to help the biomechanics of the feet. There are several different types of foot orthoses and techniques of fabricating them for clincians to use and choose from. Many people need and do gain from customized foot orthotics while some can be helped by the easier and less expensive mass-produced foot supports. Which one is right for each person is determined by precisely what is leading to the problems and just what the treating doctor suggests is right for that individual. All different foot orthotics have got diverse design features and a good podiatrist will try and match those up to the requirements of the individual. If that is not done the right way, then there might not be any improvement in the problem.
Foot orthoses are not without their issues. When they are not the right choice for the individual, then they will not help. You are also restricted by what footwear you need to use, in that you need to be able to fit them into the shoe and there might not be adequate space. There are also kinds of shoes, for example the flip flops which they simply can't be used in. This tends to pose a problem in hotter climates which make closed in footwear needed for foot orthoses uncomfortable. You can find options, as an example, the Archies that have a foot support integrated. The design of the arch supports in these flip-flops resemble what you will get in an over-the-counter arch support, but most likely not as good as what you will get from a customized foot support. Using these do give a helpful alternative to foot orthotics, depending on where one can wear them and also the nature of the biomechanical problem. If you do need foot orthotics there is no harm in trying these kinds of choices or raising it with your treating doctor to see what they believe.