What's interesting is that while this is the widespread conventional wisdom, it turns out that only the top 6-77 or so players make any statistical impact on playoff wins.
That's different than the regular season, where deep rotations can help a team get to the playoffs.
But once the playoffs start, the only players that matter is your top 6-7.
Players 8+ make zero statistical difference in outcomes. (Arturo Galleti has a
good explanatory breakdown here.)
That doesn't mean that players 8-12 don't get
some playing time, it means that their minutes have
no statistical outcome on the series. They don't play enough to impact the game, positively or negatively. And they certainly don't play enough to make a difference over a merely league average player.
I know that sounds insanely counterintuitive but the math is there.
Most, if not all, teams radically tighten their rotations during the playoffs. Depth, fatigue, injuries don't matter as much. NBA players can power through post-season series and you want your best players on the floor as much as possible.
So...I'm all for adding another quality player or two.
But that's primarily so that the top players can keep their minutes low in the regular season and be fresh for when it matters, not cause it's likely anyone the Cavs would add now would be a top 7 rotational piece.
(But of course if they can get a Top 7 rotational player, better than someone in our current Top 7, then so much the better.)