I wouldn’t call the 1981 Celtics ridiculously stacked at all.
They were stacked compared to their opposition.
PG: Tiny Archibald - All-Star, 2nd-team All-NBA, 9th in MVP voting (was 5th in MVP voting the previous year), Future HOF
SG: Cedric Maxwell - Leading scorer in the Finals and Finals MVP
SF: Larry Bird - All-Star, 1st-team All-NBA, 2nd in MVP voting, Future HOF
PF: Chris Ford - solid starter who had averaged 16ppg just two years earlier, and future HOF Kevin McHale was playing 20 mpg off the bench
C: Robert Parish - All-Star, 7th in MVP voting, Future HOF. He would have easily gotten 3rd-team All-NBA if it existed back then, but got beat out of the first two teams by Kareem and Moses Malone.
Besides Kevin McHale, they also had Gerald Henderson, Ricky Robey, and M.L. Carr coming off the bench, all of whom could have started for other squads
What other team was starting 3 All-Stars, 3 guys who finished top-10 in MVP voting, 4 future Hall of Famers, and still had a FIFTH player good enough to grab the Finals MVP?
Their opposition in the Finals was the 40-42 Rockets, the only team with a losing record ever to make the Finals. They only had one All-Star, and their 2nd-best player was 5'9" Calvin Murphy who got hurt and missed half the Finals.
The best team they played was the Sixers, who weren't ready like that yet. The Sixers's #2 was Bobby Jones and they still took the Celtics to 7.
No other team that season was stacked 3-deep, 6-deep, or 9-deep like the Celtics were.