Liverpool wanted a fresh start in 2023 but Andrew Robertson says the Reds have been "nowhere near good enough" this season and played "worse" since the World Cup.
The Scotland international captained Jurgen Klopp's side at Brighton and Hove Albion as Kauro Mitoma's last-minute strike dumped the FA Cup holders out in the fourth round.
Liverpool had taken the lead through Harvey Elliot before Lewis Dunk's fortuitous first-half equaliser paved the way for Mitoma's deserved late winner in Sunday's 2-1 triumph.
Klopp's men are out of both domestic cups and sit only ninth in the Premier League, having won just eight of their opening 19 top-flight games.
Having lost nine times already in 31 outings across all competitions this campaign, Robertson bemoaned Liverpool's abject performances that have continued after the World Cup break.
"This season has been nowhere near good enough," Robertson told ITV Sport.
"At the start of the year, we wanted a fresh start, but that hasn't happened – we've been worse. In the league, we haven't been good enough and now we're out of both cups."
The Reds' downfall may have appeared somewhat of a surprise after falling narrowly short of an unprecedented quadruple last term.
Liverpool missed out in the Champions League final to Real Madrid and saw Manchester City secure the Premier League title on the last day of the season, though they lifted the FA Cup and EFL Cup.
Sadio Mane's sale to Bayern Munich and Roberto Firmino's diminishing role should be factored in, while Mohamed Salah has failed to hit his usual lofty heights after scoring just nine goals in 19 league games.
Luis Diaz has been out injured after a promising first campaign at Anfield and signings Darwin Nunez and Cody Gapko are still settling in, yet Robertson struggled to explain why Liverpool continue to falter.
The left-back added: "It's really disappointing. You can't put your finger on one thing that's gone wrong. It's more than that. It's about trying to put a performance together where all these things click and that's proving difficult right now.
"You can tell we're not as confident in front of goal, and defensively we're still a wee bit open in certain areas.
"We were on the back of two clean sheets, which was positive, but today, two disappointing goals and they had a couple of big chances as well.
"We need to try and get the confidence back. It's easier said than done but that's the only way we can pick up results. You have to be able to score goals and you have to be able to keep clean sheets.
"We're not managing that just now and we need to do it. We keep saying that and it doesn't help the fans. I feel sorry for them, the way we're putting on a show for them just now.
"We let them down again and we're obviously disappointed to be falling out of the cup."