United, among the favourites for the competition after dropping down from the Champions League, were beaten by Sevilla in one of three cup semi-final defeats they endured last season.
Bruno Fernandes was once again in inspirational form, scoring twice as Solskjaer’s side dominated a poor Sociedad.
“We got nothing out of getting to the semi-final last year,” Solskjaer said.
“Sometimes you can say it isn’t worth it but the experience has helped this team. We have to learn on the job.
“The only way to learn from your mistakes is to correct them. The semi-final defeat last season is in the back of our heads and hurts. We felt we should have gone all the way.”
Fernandes took advantage of hesitant defending to open the scoring in Turin and then stroked in from the edge of the area for a second – which was awarded by VAR after he was initially flagged offside.
Marcus Rashford and Daniel James – who both missed several chances – then scored on the counter to leave next week’s return leg looking a formality.
“We’ve been through a difficult spell and I thought we found ourselves a little bit tonight,” Solskjaer said.
“I thought the boys had got that little bit of zip in their legs again.”
Sociedad were top of La Liga when the draw was made but were abject throughout a game played in Italy because of Covid-19 restrictions.
They failed to test United goalkeeper Dean Henderson seriously and were constantly caught out on the break by the pace of Solskjaer’s frontline.
Even Manchester City hero David Silva – who joined Sociedad last August – was kept quiet on an off night.