The history will not repeat again. I think that you shall forget it and then move on. The new era has begun. Messi has gone to the PSG and he was also become even older. There's no choice rather than giving the young talented player so many chances.
Barcelona needs to do more regeneration but it will not find the player like messi again. Messi was messi. There will be no another messi to come.
Indeed, they should do this, they should not focus on short achievements, what they should do is build the foundation for the team to last a long time. And thus they will find it easier to pursue achievements if the team is formed strongly. What I see now is that many people expect Barcelona to excel even though they have just woken up from adversity.