I can't speak for the quality of the controllers but I do know they are under paid (but that is the norm in Indonesia). Their infrastructure is mostly poor, both in the tower, upper airspace management equipment and systems and the actual radar equipment in and around airports.
Currently, ATC is split into 2 in Indonesia. Angkasa Pura 1 and 2 (AP1 and AP2) both operate half the country each. This has meant they have different training standards and equipment and thus part of the reason for your poor service. This situation is currently changing and the DGCA is moving to set up one ATC body. But as these things move at glacial pace, don't expect change in this decade). DGCA is also setting up ADSB across the country. I believe about 5 locations are already trialling this.
The training programme for most controllers is poor also. Most are trained at Curug, which is an under funded facility where instructors are paid very little. The way most education goes in indonesia is that if you want to pass, you pay for it. I have never seen this at Curug but would not be surprised if it happened. To my knowledge, Curug is the only ATC training body and is wholly funded by the Government - hence the lack of funds and wages.
Back to AP1 and AP2, these two are the main airport operators and are Government owned enterprises. They both have major leakage of funds into the pockets of their executives so the necessary funds required to invest in training and equipment don't really exist. Aside from this they are expected to pay the government a large dividend each year and AP2 I believe is the biggest dividend contributor of all Indonesian Government enterprises.
Despite my miserable facts above, AirServices Australia has been doing some fantastic work recently trianing ATC staff and assisting them to implement SMS and training programs. Unfortunatley their funding for this runs out next year. I believe one of the biggest issues facing AirServices though is the lack of commitment by senior management in AP1 and 2 to getting the assistance programmes off the ground.
Change needs to coem from the top!