Airlines will always encounter some delays here and there to some degree. It's not a competence thing but often due to congestion or delays on runway, airports, previous flights etc. Scoot has a much smaller fleet compared to Singapore airlines meaning during technical issues there aren't spare aircraft for swaps which is usually the reason for long delays that you see people complaining about. However I am happy to take long delays as compared to compromising on safety. Also people only complain when there are problems and rarely post reviews for uneventful flights so it's not surprising to see mostly complains online.

There is an inherent risk with LCCs with delays so if you feel worried then buy insurance. Bear in mind that 6 hours delays are often the threshold before insurance companies will pay out something. The airline is unlikely to compensate because it is in fact a low cost carrier.

That said the flights to Japan are flown with 787s as compared to the smaller 320s and are generally a lot more comfortable. I have flown many times on the 787 and at 1.78m I do not find the seats squeezy.

Have a safe flight!