Limitations of meditation/mindfulness without Vinaya
The basis of Vinaya is morality and taming the senses
Lack or morality (Sila / Vinaya) or hedonistic practices is based on unwholesome thoughts
Unwholesome thoughts result in unpleasantness (due to -ve fabrications and karmic formations) which is detrimental to meditation (Piti and Passadhi being an aid to meditation)
This also lead to verbal fabrication as most unwholesome thoughts lead to through proliferation which makes the mind harder to focus and also creating more fabrication.


Morality (Sila / Vinaya) is the basis of developing Samaddhi which helps developing Panna. So strong morality is needed.