Ramayana is a venerable epic about a love triangle: Sita (syota ng bida) is Rama's (bida) wife, who was abducted by Ravana (kontrabida) and eventually rescued by her husband.
Kecak is a music drama adaptation of Ramayana by Walter Spies who invented it in the 1930s for western tourist audiences.
In other words, kecak is a derivative for commercial purposes just like Nyoman Nuarta's 122-meter Garuda Wisnu Kencana statue, the tallest statue in Indonesia and the tallest Hindu god statue in the world, that was actually fabricated in Bandung before being assembled in Bali where it was unveiled by President Jokowi on September 2018.
On the other hand, traditional Balinese dance is ancient and religious, and has been inscribed as by UNESCO as an "intangible cultural heritage" in 2015.
It is as aunthentic as the superb Indonesian dinner at Kayumanis Resto in Jimbaran where it was performed for us, elevated but legitimate, unlike the post-kecak bland western menu of Jendela Bali Panoramic Restaurant.
Both led to unexpected post-performance outcomes: a freak accident on our way back to the hotel that resulted in the tragic death of a motorbike rider vis-a-vis a night cap of Bali beer (Bintang + Bali Hai + Singaraja) after arriving at Four Points by Sheraton.