As you stated: 1. Most now do not believe that ancient atmosphere was a predominantly reducing environment (as required by the experiment).
2. The energy requirement for the experiment is tremendous. It is unlikely that early Earth lightning storms would have produced enough energy to generate the vast amounts of organic molecules.
3. Recently, meteorites have been found to contain amino acids. It is unlikely that these compounds were created by the method that Miller proposed.
Item 1:
Even I have the equipment (telescope and spectrometer) at home to study the atmospheres of Jupiter and Saturn. I can identify the major "reducing environment" currently present in the atmosphere of those planets.
Who told you that the Earth did not also have such an environment when it first formed? If not, then why not?
Item 2:
This same experiment has been conducted using the low intensity light, cold temperatures and known gasses present on the planet Mars. Once again, amino acids were produced.
Even in the icy world of Neptune, complex hydrocarbons and amino acids have been found.
Who told you that this molecular reaction of hydrocarbons requires such high energy?
Item 3: Meteorites have been found to contain amino acids. If anything, this confirms how common this chemical reaction is.
Once again, I must seriously question the motives of people who have been telling you this stuff.