The presence of MacAllister and Szoboszlai is expected to cover Liverpool's midfield deficiencies next season. As a result they have ended up together with several players such as Chamberlain, Keita, Fermino and Carvalho playing in the same position. As you said fit also looks like they still need two or three more players to start next season, if all goes well for Liverpool I think they can finish in the Champions League Zone next season.
The two midfielders signing of Liverpool is a very nice move. They will surely perform well since Liverpool lacks a ball finisher like Mane in their midfield.
The main purpose why Alexis Mac is signed into Liverpool is for him to replace Mane since Nunez has not yet fit in the missing spot of Mane in the Liverpool team. On the other hand, Dominik Szoboszlai will act as support for midfield from the right wing. Liverpool's midfield will now be made of Alexis Marc, Gakpo, Salah, Dominik Szoboszlai, and Nunez. Liverpool can bring in one more additional midfield player if they want to but the midfield combo they have is okay for next season's upcoming matches