The biggest problem for me is that flat from the end of the Biche descent to Culoz, but I assume Culoz is paying so they can't do the Anglefort side. Really, there's nothing wrong with this mountain, it's inconsistent and offers more than enough incentive to race. However, with Bernal and Quintana distanced early, everybody else was just happy with where they sat and let Jumbo ride tempo into everybody. This climb has produced great racing several times in the Tour de l'Ain, but the Tour de l'Ain doesn't have as deep a field so the domestiques aren't as strong, and the Tour de l'Ain, being a smaller race, doesn't have the same importance paid by sponsors to minor placings, so going out to try and win is more important than preserving a good-but-not-great placing, and so there's less reason to be afraid of losing. That's been one of the Tour's biggest problems from a racing point of view as long as I've been watching the sport - the importance of a good placement is such that not losing time is more important than gaining time, leading to more conservative racing than you see elsewhere. In 2010 you had Vaughters put Zabriskie and Millar on the front and gun the péloton because the break had Plaza and Horner in it and their time gap threatened Ryder Hesjedal's 10th place (which he promptly then improved the next day while Plaza and Horner lost loads of time, tired from their break escapades the previous day). You had Pierre Rolland attacking IAM Cycling a few years ago because they chased down an attack of his so they could defend Matthias Fränk's 14th place. 14th!!! That kind of thing doesn't happen at the Tour de l'Ain for obvious reasons.
That said, there are plenty of platforms to work attacks from on this climb and I don't believe that every single rider in that group outside of Jumbo was absolutely at their limit. However as Jumbo were only using Dumoulin and then using Kuss to block people from getting further forward (not literally like Rabobank in the 2014 Giro Rosa, no, metaphorically), everybody was too afraid that any attack even if they dropped Dumoulin would be chased down by Kuss, so they just let Dumoulin pace them all the way up.
And whereas people came up with excuses for the soporific, disinterested racing on stage 6, the subsequent stages were the explanation. Tomorrow's a rest day. Realistically everybody was simply happy that with Quintana and Bernal dropping they had either gained 2-3 places (depending on where they were relative to Martin, too), or eliminated 2-3 competitors, so it never even occurred to them to do more, they'd already got a positive outcome from the day. That's the riders, not the climb.