Looking ahead at the post-ASB schedule (yeah, I know). As per Tankathon, opponents winning percentage of 0.464 is tied with the Heat for the 3rd easiest, but that is not the entire story. 12 games at home, 15 on the road.
They actually have a difficult stretch coming out of the break. Open on the road against the Bulls; being on the road is probably a good way to resume play. Followed up with a visit to Madison Square Garden. Then a home stretch against playoff teams Philly, Dallas, and nemesis Golden State. Then a 5 game western swing which opens in Cleveland, and includes stops in Denver and Phoenix and a Portland/Utah B2B. Their post-trip homecoming game (aka, chance to bet against the home team) is against the Suns.
That one-game homecoming is then followed by a road/home B2B against the Wizards and Pistons, the latter another potential trap. Giannis then comes to town, after which the Celtics embark on 6 game trip. That trip includes a road B2B against Pistons and Bulls, a weird 2 game stop in Atlanta with 2 off days in between, a visit to the Big Easy on Easter Eve, and a game against the only Eastern Conference team the Celtics haven't beat. Then they return home to face the Thunder, another tough matchup in a historically bad game situation for home teams. They end with 6 of 7 at home, the one roadie being a trip to Mount Giannis.
As noted above, going 16-11 gets them to 59 wins and is likely good enough for #1 seed overall (and almost certainly enough for #1 in the East). And there should be 16 wins in there even with the inevitable games with 2 or more starters resting. But there are definitely losses baked into this schedule, and there should be enough losses in there to get people to complain about the team's "toughness" and "reliance on the 3".
Tl;dr: the Tankathon numbers tell only part of the story, and the team will lose some games that make us think WTF?