The reigning Premier League champions are set to finish at least 19 points worse off than their 2024/25 total and are still not certain of a top-four place with two games remaining.
A win against Aston Villa at Villa Park on Friday would help secure Champions League qualification, something Van Dijk says must be the minimum target.
"We have been below standards as a club on the pitch and that is something unacceptable," he said. "It's down to us to make sure next season we are not in a situation where I'm saying this again."
Despite the disappointment, Van Dijk insisted there is still responsibility to finish strongly. "For now we have a duty and responsibility to finish the season in the best way possible," he added, pointing to the importance of securing Champions League football.
Looking ahead, the Dutch defender also addressed the expected transition at Anfield, with key figures including Mohamed Salah and Andrew Robertson having played reduced roles this season amid talk of long-term squad evolution.
"There is a transition going on, and influential players are going to leave," Van Dijk said. "You can't fully replace someone like Mo in terms of quality. Someone has to become their own version and show their quality."
He added that change is inevitable in football but must be managed carefully: "It takes time because of the standards they have set. It's a challenge, but you should embrace it and use it as fuel."
Liverpool now turn their focus to the trip to Villa Park, knowing the result could define the final direction of their season and shape preparations for a crucial rebuild ahead of 2026/27.
Seamus Coleman has confirmed he will bring the curtain down on his playing career at Everton when his contract expires next month, closing the book on more than 17 years of service at Goodison Park.
Mikel Arteta has insisted Arsenal will block out the title race noise and focus only on beating Burnley when they return to Premier League action in their final home match of the season on Monday.
Chelsea interim head coach Calum McFarlane believes Joao Pedro and Cole Palmer are ready to shine when the Blues face Manchester City in Saturday's FA Cup final at Wembley.
Manchester City manager Pep Guardiola has revealed his FA Cup final plans after rotating heavily during Wednesday night's Premier League win over Crystal Palace.
