"We've got to fight next season," the 25-year-old Slovenian said, adding that the example of the Celtics themselves -- back in the winner's circle after falling in the finals in 2022 then missing out on the title series last year -- was one to note.
"They're a great team," Doncic said. "They have been together for a long time, and they had to go through everything, so we've just got to look at them, see how they play, (they have) maturity, and they have some great players.
"We can learn from that," Doncic said.
Doncic spearheaded an often sluggish Mavs offense throughout the series, despite playing with nagging knee and ankle injuries and a painful chest contusion.
"It doesn’t matter if I was hurt, how much was I hurt," said Doncic, who scored 28 points in Monday's game-five defeat that saw Boston clinch a record 18th NBA title.
"I was out there. I tried to play, but I didn’t do enough."
Having extended the series with a game-four blowout, Dallas never led on Monday, trailing by double digits throughout the second half.
But Mavericks coach Jason Kidd said just booking the title showdown with the 64-win Celtics -- a year after Dallas failed to make the playoffs -- was a harbinger of what this Mavs team can accomplish.
"This is just the beginning," Kidd said. "A lot of people -- excluding the people in the locker room -- didn't have us here.
"Yes, we lost 4-1, but I thought the group fought against the Celtics and just unfortunately just couldn't make shots."
As the game ended, Doncic exchanged an embrace with teammate Kyrie Irving, an NBA champion alongside LeBron James with Cleveland in 2016 who was brought in to bolster the Mavs in February of 2023.
"We said we'll fight together next season, and we're just going to believe," Doncic said.
The Mavs' post-season push was buoyed at the trade deadline by the acquisitions of P.J. Washington and Daniel Gafford, and guard Josh Green said Dallas has the raw materials to challenge again.
"I think we got here and everyone is hungry now and obviously we didn't get what we wanted. We need to regroup and be back here again next year," Green said.
Added Irving: "Failure at this stage definitely sucks. It's a bitter feeling because you want to keep playing and you feel like your best game is coming up next.
"But I'm grateful for the opportunity to grow with these guys in this locker room, and everybody across the organization."
