The best software is the software you and your team understand best
As complexity increases, an RTOS or other structured framework will help you in managing the complexity to achieve reliable operation
RTOS-enabled products are all around you (e.g. MHX-920A, MHX-2420)
Complex monolithic software is hard to understand and even harder to maintain / grow. Strive for modular software. Build, test & verify incrementally. Don’t forget to backup.