Not true at all. Cannes is one of the best and most influential film festivals and is regarded as such by the industry because it's about quality filmmaking, not campaigning. You only have to look at the calibre of the juries and the very diverse line-up of films in competition to see that.
The 'glam' factor has always been an integral part of Cannes - go there, be seen, party, - and yes, that increasingly attracts those at the lower end of celebrity in need of some red carpet coverage - but it's all part of the Cannes experience and takes nothing away from the competition side of it which is as professional and respected internationally as ever.
So why is Chloe Sims at Cannes????? perfect example of what the OP was pointing out me thinks....