I'm one of those people who loved the 2008 team (and the whole KG/Pierce era) but I think it's too easy to criticize the current team, because this is a totally different era.
Offensive basketball has totally exploded, and you just can't play the "grit and balls", grind-it-out style of those old Celtics teams. So, when these current Celtics are up 13 and see a mega-explosive offensive team like the Pacers close the gap, I don't think, "Oh, the 2008 team would have never allowed that", but rather, "This is basketball in the year 2024."
In hindsight, old championship teams are always remembered as less flawed than they really were. If the 2023-24 Celtics win this title, I'm certain the same thing will happen when they are discussed 15 years from now.