In my opinion, Alexis Mac Allister is not enough for Liverpool now, unless they are willing to gamble by relying on the players in their current squad.
We must recognize that Liverpool did a good transfer, bought a good midfielder, to improve their squad. Mac Allister is good for them in defensive and attacking contributions too. He will be a combine of Fabinho and Alcatara, two in one.
Virgil van Dijk this season he has not played at his best, several times he could not anticipate the attacks that were coming for Liverpool, even several times the goals came from his mistakes in anticipating the ball. It's normal, but what happened this season in my opinion is too often. I hope he can get back to his best this coming season.
Don't forget that Van Dijk got a serious injury and I will be realistic that with effects from that injury and ageing, Van Dijk will no longer play outstanding like his best season for Liverpool years ago when he was like an unbeatable defender, the best one in that season.
Liverpool must ask their scout team to find other central defenders to replace Van Dijk too. Replacing him is not easy and will need time to find good central defenders on market and make deals.
The performance of their 2 full-backs this season has also not been so optimal, their transitions are often late when Liverpool carry out attacks or counter-attacks so that it creates empty space that opponents can take advantage of.
Arnold will be used in midfield like Klopp and Southgate tested recent months. Such positions maximize passing and creative skills of Arnold, it is better for him and for his team too. I believe Klopp will use Arnold in this way in a new season.
They will need to secure the defense at two swings and reduce conceded goals to compete for titles. At least with a change of position for Arnold, their swings will be stronger in defense.