There are lots of reliable science done using EEG and fMRI; I believe you learned the wrong lesson here. The important thing is to treat motion and physiological sources of noise as a first-order problem that must be taken very seriously and requires strict data quality inclusion criterion. As far as deep learning in fMRI/EEG, your response about overfitting is too sweepingly broad to apply to the entire field.
To put it succinctly, I think you have overfit your conclusions on the amount of data you have seen
To put it succinctly, I think you have overfit your conclusions on the amount of data you have seen