Dortmund had looked set to prevent Bayern from claiming a seventh successive crown last term after they led the league for much of the season, before crashing to a 5-0 defeat to their title rivals late on to blow their hopes of winning the championship.
Alcacer broke the league record for number of goals scored by a substitute in a single season when he netted in a 2-1 defeat against Fortuna Dusseldorf, taking the record from former Freiburg striker Nils Petersen.
And the Spain international says he feels ready to win a more regular place in Lucien Favre’s team next term as they seek to finally wrestle the Bundesliga crown away from champions Bayern.
"I do not like to sit on the bench because I'm a very ambitious person," Alcacer, who turned his loan move from Barca into a permanent deal with Dortmund in February, told Sky Sport .
“I'm a happy, funny person, but when I'm sitting on the bench, I do not like anything anymore, then I'm a complicated guy, which I do not like."
Alcacer also lamented that "in almost two years I have not started three consecutive games," and claimed he has "worked incredibly hard" during the summer break to ensure he doesn’t continue to miss games for Dortmund.
"We were so close to winning a big title - and in a relatively easy way. Football has its own funny moods and we did not make it," said Alcacer. "I try to help with my goals and that we can climb one more place in the table."
The 25-year-old joined Dortmund, initially on loan from Barca, at the start of last season, and has netted 17 times in Germany despite his lack of opportunities in the starting XI.
He has featured 15 times for Spain, and received his first call-up in nearly two years in October 2018 shortly after swapping La Liga for the Bundesliga.