Actually one of the things that affect most clubs is lack of planning, though in as much as they would already have all the kind of players they needed but planning ahead of time is always one of the most important thing because majority of clubs has been going through a lot because of the inability to have put things in place, so actually just like you said since Mohammed Salah is the most valuable and the most experienced player in Liverpool what the team management supposed to have been doing is to be striving for a good player that would replace Mohammed Salah because already the club management knows that Mohammed Salah will not play for Liverpool till he retired so working on those things now should be there number one priority because if Mohammed Salah leaves the club without any replacement Liverpool will seriously be affected before they would get use to it.
Look at Lampard for example, he was a good players and was well respect, had a good time in Chelsea but loo at his career since he signed up been a manager, he has never achieved anything serious in his career, this is to say not all great players make good coach and not all good coaches were once a player in their life time. There are some of them that never play for any club and yet they are good because to coach is another talent on it own.
Of course not all great players make a good coach but in most cases people believe that since a player was very good during the time he was playing he will actually have a good quality of a coach forgotten that there is no how they can compare those coaches that follow the right process, so actually in the case of Lampard indeed he was a good player during his time but that wasn't enough to immediately go into coaching without much of a coaching experience.
However let's use Arteta for instance he was an interesting player when he was still playing for Arsenal those days but after he retired he decided to go for coaching and since he knew that coaching is not an easy task because it involves critical thinking and bringing a good strategy that would work very well for the players, he decided to work under Pep Guardiola because Pep Guardiola is a very experience coach and after acquiring the kind experience he needed, you can see he is now doing very well and now he is actually one of the best coach.