Well, Arne Slot really should think about this earlier before it's too late. But Liverpool's squad since the Klopp era has been like it is now and actually this team has quite good second tier players. Remember last season M. Salah was injured for a few weeks or longer but Liverpool was still good because the team's second tier players were quite good. But when facing a team that is quite weak, it would be better for Arne Slot to limit the playing time of the main players more. They can be played from the early minutes to lock in a scoring advantage and then pull it out in the second half and give time to the second tier players. This must be done in a busy match schedule. But I also understand that we know that in the Premier League the competition is very tight and there is no team that can be considered weak. But in the UCL I think in the remaining matches Liverpool can relax more. They just need to lock in winning points to qualify for the next stage and let the remaining matches be played by the second tier players. And playing the main players again in the round of 16.
The depth of the squad is indeed very important for the club because if there are injuries to several core players it will affect the team's performance in facing the competition, especially if Liverpool currently has a fairly tight match schedule that they have to run. The squad owned by Arne Slot is a player left by Jurgen Klopp and there may not be much change if they do not try to make some efforts to recruit new players in the upcoming transfer market and Liverpool also need second-tier players to help them compete in the Champions League and the Premier League.
Liverpool is much easier to qualify for the next round because they are in the first standings table so there is no big burden to qualify for the next round. But the problem is when going through the next round because there will be a lot of competition that they might face in the future.