It's not just GC riders. It's every rider who isn't a sprinter.
The Tour has become a bizarre unbalanced spectacle in which interminable transition stages are dominated by a dozen sprint teams, all with riders working for their sprint leader. No TV breakaways anymore either. Just a bunched peloton heading towards the inevitable bunch sprint whilst dodging street furniture which is more or less just left there to cause some chaos for the evening news headlines.
Then all the high mountain & medium mountain stages are now GC stages. Breakaway riders (usually GC riders who've dropped so far down in the classification they need to try & save something with a stage win) need to get very lucky to resist the Tour favorites.
And... that's about it.
This year I think thats a route problem. It was very obvious this year's route was very unbalanced in terms of what you're referring to, and the Tour rightly got critisized for being to one-side (two sided, I guess). That said the opening weekend proved to be the stages that you actually were gonna gun for, and while that was a bit unexpected, its also on the riders for not trying a bit more on those stages. The breaks formed relatively early, and it was obvious that it would take a big effort from a team to actually reel them back. The same thing can actually be said for stage 12. Way too many teams did not invest anything, and stage 13 was, yeah well, pure coincidence that it ended like that given that the whole peloton more or less was trying to get in the break.
But I agree with your overall point. The only bang on break stage is actually stage 18. I think with this GC, stage 17 is also going to the break, and then stage 19 and 20 is still up in the air. And then we should expect (and demand) teams to actually try to join the break on stage 16 even though its completely flat. Otherwise these complaints also feel a bit weak if they're not even really trying on these stages. But it mostly falls down on ASO for a weak route IMO. Something like 2022 should be the norm.