Liverpool has a great team, and I agree with you that Liverpool doesn't need to do much in the transfer window since they have a good squad that can compete in the UEFA Champions League competition and the Premier League or any other competitions they will play next season.
Liverpool are having a great squad right now, but they are still having some lapses, so slot will still have to sign more players to strengthen the team’s performance by next season. Liverpool was sent out of the FA cup final by Newcastle, and they were sent out of the Champions league by PSG, so we can see that Liverpool have a good squad right now, but they still have to sign more players.
Liverpool were able to win only the premier league last season, am sure Liverpool will want to win the premier league title again by next season, and they will want to win other titles also, so they should try and sign more players to improve the teams performance.