Standing in for the suspended Luis Suarez, Alcacer's strike in the third minute of first-half stoppage time put Barca 3-1 up against Alaves at Vicente Calderon and proved to be the last goal of the match.
Alcacer does feel he has improved as the campaign progressed and was thrilled to end it on a high, but understands he alone will not decide what happens for 2017-18.
"I only live in the present and I'm happy here," he told reporters after the match.
"It is not up to me to decide what happens next season, it is the directors and the coaches.
"In the end, the hard work was reflected on the pitch. Helping the team with a goal is important and I am very happy to end the season like this.
"I have gone from down to up during the season. I always try to think in the present and on the next game and, in the end, it has its rewards.
"You can never give up - you must always give your all."
3 - Neymar is the first player to score in 3 consecutive Copa finals (2017, 2016 and 2015) since Ferenc Puskás (1962, 1961 and 1960). King. pic.twitter.com/yfbvuJ9Bbm— OptaJose (@OptaJose) May 27, 2017
Lionel Messi, who had scored Barca's opener, set up Alcacer's goal and the 23-year-old paid tribute to his star team-mate's influence on the rest of the squad.
"There is no better player that Leo Messi," he said.
"I am very proud to be able to live and learn beside him. It is amazing the ease with which he plays. He makes football so easy. There is no doubt that he is the best player in the world."
Alcacer completes the season with eight goals from 27 Barca appearances in all competitions, although just 11 of those outings were starts.