Barcelona lost to Inter in the semifinals only because they were rushing and didn’t take advantage of their chances. Inter relied on their experience and waited until the end. I think if Barcelona had made it to the final, we would have seen a much better match than the one between PSG and Inter. Inter looked very bad and physically unprepared.Regarding the players, as you mentioned, if someone gets injured, of course they need to have good players on the bench. I believe Barcelona’s management will make some very good moves in this transfer window.
It wasn't about rushing, both teams played good. Barcelona and Inter have their style of play, in all the games they played in the Champions League, including their domestic league, go in the same direction. Barcelona plays quick football, possession starts from the back using all their squad, which is a tactic from the side. Inter Milan plays all defensive and attacks only with key players, the difference in their formations gives an advantage to the opponent, watch how PSG understood and followed a different pattern.
If Barcelona joins all teams to improve their balance, especially defensively they should have a spot to compete in the Semi-final and will probably make it into the finals.