I`m not a fan of sportives but putting that aside I dont see why the organizers need to put warning signs up at junctions telling you to slow down or stop etc when there are official roadsigns there as well .These signs will then get left up for months and litter the countryside with neon yellow

but putting that aside

I think you might need to put some more effort into that

Terrified of litigation (and quite rightly).
Organisers are simply covering themselves against claims.

And of course most organsiers do take their signage down. One organiser I know offers a free ride in any of his events if any cyclist finds any signage from a past event. He’s never had to give that free ride yet!

One particular sportive around here leaves signs up after the event, sticks directions on signs and seems to add to it year on year.

There are several sportives around here, but its the only one that doesn’t clear up.

Deleted.
I am a bad person and should stop taking the mick out of Sportiverists.