I agree that we will pay a lot of money to replace Neymar, and that, whoever we sign, will be a downgrade, at least on paper if not in practice. Barcelona at this point are forced to trust in their La Masia more, and to me, that is a plus. Yes, most likely we'll not find a new Xavi or a new Messi there, but the reality is that we don't need to. Just look at Madrid and what they've done with Casemiro, who, let's be honest is not at all a special talent of any kind.
I look at Sergi Roberto, and he is improving every game. In 1 year he could be a starting midfielder with absolute ease, and he has already played amazing in two back to back clasicos on Bernabeu (4-0 and 3-2 wins). I see Alena and in 2 games he has shown the kind of maturity that is far beyond his age. He is potentially a future great midfielder.
More than losing Neymar, what is hurting Barcelona is signing players for a lot of money that just aren't better than what we can supply with our Academy. Roberto is a better midfielder than Gomes/Arda and is possibly better than Rakitic as well. Alena needs to play at this point, he just oozes talent. If the new manager makes the right moves, Barcelona will build a new generation. Messi and Suarez have 4 more years of top football in them. Yes, we've lost Neymar, but it's very likely that a new young star will come in his place, be it Coutinho, Dybala, Dembele, Mbappe or whoever. Not as good as Neymar, but not only the better players form the better team. The greatest trio in the world didn't give us a single goal vs Juventus. They all played pretty shit. Other things count more, it's not always that the best players will form the best team.
As for the rivalry with Madrid, they've just won their first title in the last 5 years. Sure, they could enter a dominating period with this recent CL - La Liga double, but let's not forget that a lot of their core players are approaching 30 years old or are already past that, like Ramos, Ronaldo, Modric, Benzema. That's arguably Madrid best 3-4 players. They need to change their leaders as well, as they naturally age. They're very much in the same spot as we are, but the difference is they have the momentum. This momentum can or can't lead to a period of domination for them in Spain. We shall see this season.