#1 Tactical point of view:

Neymar’s profile doesn’t match exactly what Barcelona need right now. Nobody can question Neymar’s ability with the ball, but the Blaugrana need someone who can lead the line up front, more like an number 9, not a number 10, surely.
With an ageing spine of the team, Barcelona have to replace Suárez as soon as possible with a world class striker, not a player of Neymar’s profile. The Blaugranas need a player who can make those runs behind the defense, who can play on the shoulder of the last defender, someone like Mbappe.
In essence, the Blaugranas need an out-and-out goal scorer, who will guarantee them more than 20 goals a campaign.
If Barcelona manage to sign Neymar then it will cost the Catalan giants huge amount of money, plus Dembélé maybe, which in turn will block the road to sign a world-class striker, given the restrictions of European Fair Play rules taken into consideration.