If he improves, Dumoulin beating him in an ITT is far from a sure thing imho. He finished as far from Dennis in 2019 as Dumoulin the year before.
I'm also not sure concerning one day races. It's not like Movistar wanted to let him ride. They simply couldn't follow. Like Masnada, like Campenaerts, like Wellens... If he goes 30k from the finish, who is going with him? Team leaders will want to wait, but what if their doms can't bring him back. High profile riders can mark him, but might need to get out of their comfort zone.
I think he'll start the season better than last year. I can see him winning San Juan this year, and he surely can get a medal in the OG and/or WCC ITT.
The thing is, not unlikely van der Poel, it's dangerous to keep underestimating him. Last year i wasn't the only one saying it would be great if he could win a short ITT in a 3rd tier 1 week stagerace... And every time we said, he wouldn't be able to pull off a stunt like that again... That the others in the peloton would know him by now. First his stunt in Hammer Limburg, then Baloise Belgium Tour, then the BNC ITT merely 7s behind Lampaert, then Adriatica Ionica, then San Sebastian, then ECC ITT gold, then his stunt in Germany where Ineos needed motorpacing to bring him back, then the WCC ITT...
Every time us saying, what he did previously was impressive, but surely the next thing would be impossible. Until it wasn't.
His win in San Sebastian is being overlooked imho and it's up there with Mathieu's win in Amstel. As a physical feat, i rate it higher (coming back on the penultimate climb after a mechanical, attacking and choking the opposition to win solo).