A few factors were at play in baku in terms of overtaking ability:
Most cars are converging on very tiny rear wings because floor is generating larger amount of overall downforce, so you don't need as much wing. Makes cars faster in general, produce less drag and thus less slipstream, and lessens drs effect.
FIA with their tunnel vision was looking at how RB flies past other much slower cars when DRSed and for some stupid reason decided to shorten DRS zone by 100m, instead of elongating it by as much. In the end it made no difference to RB but hurt all others.