What would you suggest?

Most gates handle various aircraft so a permanent fence isn’t plausible.

A moveable fence might work but could get blown around by wind unless it’s weighted down sufficiently, then it’s harder to move quickly.

What happens if you don’t have enough crew to move the engine fences, you aren’t going to deboard the plane? Airlines already struggle to have sufficient crew for the ramp, this would exasperate the staffing issue.

But at the end of the day, if you just got knocked down by the exhaust, why the hell would you walk in front of the engine.