The Celtics lost 89-101 to the Bucks in the opening game of the Eastern Conference semifinals series, something that happened after the Celtic swept the Nets in the first round of the series. In the first round of the series summary, the Celtics were very good at limiting Kevin Durant and Kyrie Irving on the defensive end, which also allowed the Celtics to easily sweep the Nets in this game.
So after the Bucks can easily beat the Celtics, it's enough to prove how far the Nets are from the championship trophy. After the Celtics lost the game against the Bucks, former NBA player Richard Jefferson deliberately compared the game to the Celtics' series against the Nets:
"The Celtics are really a good team, but it also shows how far the Nets are from being contenders."
Durant and Irving did have very good offensive performances in the first round of the series, but the Nets also have major flaws on the defensive end, which is a problem that the Nets have had throughout the season. The Nets have averaged more than 112 points per game this season, which is actually a performance comparable to the Bucks, but on the defensive end, the Nets are still far from the Bucks.
In contrast, even against a team like the Celtics with excellent defensive end and physical talent, the Bucks can rule the Celtics with stronger defense and better physical talent, which is enough to prove that the Nets and the current Bucks are not the same level of team at all.