As I understand it, already at the stage of play-offs for the right to play in the 1/8 finals, maybe we will see epic matches, for example, United - Barcelona, if United cannot take first place in their group. It will be interesting to watch such high-profile pairs, and in less balanced ones, almost all representatives of the Champions League will most likely win, like last year.
This will still happen because indeed if Manchester United cannot take over the top spot from Sociedad it is clear they will be in a bit of trouble because they inevitably have to prepare to face a club that was thrown out of the Champions League and now Barcelona is still the biggest possibility to return to the Europa League for second time in 2 seasons in a row.
It’s a pity that if United can still take first place in the group (in fact, for this they will just have to beat Sociedad with a score of 2-0 in the return game), then Sociedad and Barcelona will not meet each other in any way, since the draw for the play-offs takes into account countries and breeds clubs from one country. But in the later stages we will definitely see something interesting like Arsenal - Barcelona.