Europe League level you are right.
No, CL level as well.
Ansu Ferran and Dembele is an elite trident
People just don't realize
i) how clinical Ansu is
ii) how exceptional Dembele is in creating havoc and de-stabilizing defenses.
iii) how with the above 3, the team has all the elements of an elite attack (dribbling, quickness, penetrating, off the ball movement, assisting, finishing) and you don't have to look elsewhere
Not only you don't need Lewa or Haaland, but bringing them in (especially Haaland) would strip the team off of some of the elements mentioned above.
Who would you drop to play Haaland?
Dembele? Then you lose all dribbling, penetration, creation, and unpredictability
Ferran? Then you lose off-the ball movement, destabilizing defenses by positioning
Ansu? then you lose certified finishing, combined with comfortable positioning starting out wide
(BTW when I argued against Haaland's transfer, I compared all the goals Haaland scored at BvB until today with all Ansu's goals at Barca till today, and Ansu is much more capable of finding the net in congested settings and from difficult angles)
We just need to make sure the depth options are there to give them rest and rotation.
Both Auba and Adama are rotational options IMO for next season. If the other 3 are fit, they will start from the bench all important games.
PS:
All the above, still holds if Dembele goes, and we get Raphina.
IMO Ansu-Ferran-Dembele > Ansu-Ferran-Raphinia,
but even with Raphinia you get almost identical qualities as those of Dembele