Barcelona is delaying this deal, they are supposed to be done by this because the player get more hype after the just concluded EURO 2024. Many teams are targeting the player including Arsenal, but I think the player is interested in joining Barcelona especially as their partnership with Lamin Yamal in the EURO 2024 gives a better result.
If Barcelona is able to sign Niko Williams, it will be easier for the team and they will not be less competitive as we may think and they can challenge for the Laliga title alongside Real Madrid because these young players can do everything to win match as we have seen in the Euro 2024.
You know Barcelona is still in the financial battle and are not done with that yet but nevertheless, they may not allow that get in their way to building a good squad for next season, so far Barcelona have been making really interesting moves, though that with Niko Williams is inconclusive yet but they are very keen about it and it's very likely it will pull through and like you mentioned, it's going to be a sleek combo with yamal and the fact that the guy loves Barcelona already will get him to putting in only but his best and nothing short of it.
To bring in Nico Williams, Barca must have a lot of considerations regarding everything related to player salaries and other needs that must be spent to build a stronger club, even though most fans want Barca to continue recruiting Nico Williams, but it won't be as easy as we imagine.
I believe that if this player can join Barca, the club's performance strength will no longer be in doubt to compete for the LaLiga title, but the problem is that Barca must have other alternatives to get more money to cover other costs.
Barca does not have to force themselves to spend large amounts of money on just one player, but it could have a negative impact on the club's financial future which cannot improve immediately.
We can only hope that in the near future there will be investors who provide funds to Barca to be able to bring in this reliable player.