Wirtz is not a top striker like Nunez to replace him in that position. He is an attacking midfielder and if they have a better striker, it would have been better for them than relying on Wirtz to replace him in that position. I don’t think that signing is for a striker role, but for an attacking midfielder. There was rumours sometimes that Liverpool will sign Isak from Newcastle, if that happens then that will be the best replacement for Darwin Nunez.
Even though Wirtz is not a striker to replace Nunez, since Nunez has not done so much for Liverpool since he arrived from Benfica, it is okay if Liverpool uses Wirtz as Nunez's replacement because I believe Wirtz will be more useful for Liverpool than Nunez. Liverpool should just forget about signing Isak from Newcastle United because they will never succeed in that deal because Newcastle United is owned by Saudi Arabia's Public Investment Fund (PIF), and there's no amount of money Liverpool will offer Newcastle United that will make Newcastle United allow Isak to move to Liverpool.