In the sense that they do not have a top 10, MVP caliber player on the team, yes.
I think it's fair to say that historically, teams that lack a MVP type talent, irrespective of their point margin and their regular season win totals, don't hold up as well against elite opponents in the playoffs.
The 2004 Pistons won a championship without an MVP type talent.
Billups was the best player on that team.
But that Billups led team went to the Finals twice.
That Pistons team had the right mix of players.
They had inside presence with the two Wallaces.
Billups, Rip Hamilton, and Tayshaun Prince took care of the scoring.
The Celts should model that team instead of the GSW model of Steph and Klay.
A Celtic team with a starting 5 of Kemba, Brown, Tatum, Gallinari, and Steven Adams will be similar to the talent level of that of the 2004 Pistons team.
Smart and Theis come off the bench.
EVERYBODY uses the piston team of an example of a team winning without a superstar. You know why? Because it’s pretty much the only one. It is far and away the exception to the rule.
Let's use other legit contenders then.
1975 Warriors - No MVP either but you can argue that Rick Barry is an MVP caliber player
1979 Sonics - No MVP either. Their best player? Our own Dennis Johnson
89-90 Pistons - No players who have won MVP. Their best player, Isiah Thomas have never won one and they went to repeat.
1996 Sonics - Came close against 72-10 Bulls, winning at least 2 games in the finals
1994 Knicks - 1 game away from winning against the Rockets in the finals, if it wasn't for Sam Cassell dagger and John Starks pulling a major choke job.
2000 Pacers - Probably the best finals opponent the 3-peat Lakers have faced. Winning at least 2 games against them.
2002 Kings - No cigar but they were arguably the champs that year if it wasn't for scumbags like Donaghy.
2019 Raptors - You could argue that he is an MVP caliber player. But with constant load management, he makes it difficult to win MVP trophy in the future.