Rakshasa wrote:What I mean is, do each of them have to be completely mutually exclusive?
No. Each has aspects that the other has and does require.
In order to practice shamata there has to be a level of mindfulness (sati) to detect and counter distractions immediately.
In order to practice Satipatthana there has to be a level of shamata (calmness and concentration).
In order to practice Vipashyana a level of both, shamata and mindfulness, is required.
Rakshasa wrote:If yes, shouldn't Shamatha directly lead to Vipashyana, ...
No because the dynamics of dependent arising is missed because shamata as stand-alone pratice is merely static concentration.
Rakshasa wrote:In other words, practicing Shamatha is the only requirement to gain enlightenment?
No, actually Satipatthana is the only complete way in itself because it has all aspects required: shamata aspects calmess and non-distraction, sati and vipashyana.