I agree, of course Messi will always be the best player while he is at Barca but he didn't carry the team last season as you correctly said. I thought he had a good season but not a great one by his standards. I felt his best game was the 3-2 victory at the Bernabeu and the only big game where he performed well last season. The Ramos red card obviously helped and really decided that game. Lastly, In the 6-1 game against PSG, I thought he was pretty poor and didn't show up except from scoring the penalty.
Barca have too sign two worthy replacements in place of Neymar or they will waste away Messi's last few good years because he can't do it on his own anymore. He is 30 years old and he is only going to decline from here on out. I am afraid that he might save himself for the WC qualifiers and finals and not give his all for Barca because this upcoming WC will be realistically the last one he can win. Barca need him to be at his absolute best if Barca going to compete for La Liga and the CL, even more so with Neymar gone.