I think it gives the members more versatility to show what they can do. Idols are good at different things and I feel like with positions, it causes fans to fight over who should have more screentime, more lines, etc. based on their positions. Without them, it gives them sort of free rein.
And positions were mostly based on what the member excelled at and it was kind of flawed in a way because those are the positions you debut with and everyone can improve in what they do.