Playing music without any 'technical knowledge' is possible, and not as fatal as driving a car without knowing how to handle a skid (front or rear), knowing just how far it takes to brake in varying road conditions, etc, but there are many "things you never dreamt of, Horatio!".

Scales ARE the basis of classical music, you practice the finger movements (including turning the thumb under on the piano) to get from each note to the next one for each scale. You also practice arpeggios, which are the basis for 'simple chords'. Scales are good for pitch training for singers too.

You also get specially written exercise books designed to strengthen each finger movement (like the Ricardo Iznaola concepts mentioned above). Can't remember the exact name of the concept now, but the original ones were for piano - and you can get them for piano accordion too. As a mainly keyboard trained guy, I suspect that there are similar books for most other instruments too.

The BASIS of 'classical music training' is to know 'all the twiddly bits' of music theory, so that you 'just use them' - one of the reasons that classically trained musos often seem to look down their noses at self trained and folk musos who often seem to not want to understand where the classically trained muso is coming from. OK one is not forced into the 'mould', but ignorance is not really bliss!