This discussion about him not be able to build his base level before his season seems to be nonsense. He refused to came back earlier in order to build his shape calmly in March and April until he started his season in Fleche Brabançonne.
It seems way more plausible this lack of performance in the mountains is due to his team not be able to develop him correctly. They can't figure what weight is ideal for him in a GT, they can't put (I'm not even asking for a good team) a decent team around him and everyone is underperforming, even those who had a perfect winter.
Remco is still kicking everyone's ass in flat TTs (he probably did a top3 performance ever in the Dauphine's TT) and he was very strong in Ardennes (his LBL was a mental bonk for sure). This is not lack of base level. Lack of base level is what Remco had in the Giro 2021, he started somewhat strong but was clearly fading when days went by. In this Tour, we didn't have a proper stage in the first week to acknowledge his true level.
He must leave Soudal now, he is wasting years by riding in this team.
Other thing very important is his mentality. He needs to manage his expectations way more. He is not the top dog like he was in his junior career, he needs to understand he is not on the same level of Pogacar (for sure someone will call me a Pogacar's fanboy and this is a load of crap but I don't care), why doesn't he go to races where Pogacar isn't there? Build some confidence, win some races, try to fight for a Giro, some one week races (he never won one) and go to races like MSR, LBL, GdL more relaxed, without trying to outpower Pogacar because he can't most of the time.
I know the Tour is his dream but he needs to realize he is miles behind Vingegaard or Pogacar. He is happy with a third place for the next 3 or 4 years?
Lastly, he needs to improve his bike handling, try to regain some confidence in the bunch by racing more "less hectic" races. He can't have this liability, specially when he is the secind best in classics/monuments.