We're not talking about "ideal" big men though. Yes there are "unicorns" out there like Jokic and Towns and guys who are paid a lot for what they are, like Millsap. But useful big men aren't that rare.
Lopez, Ilyasova, Mirotic, Ibaka, Siakam, Gasol, Turner, Sabonis, Boban, Adams, Noel, Grant, Plumlee, Lyles, Harrell, Zubac, Gobert, Favors, Nurkic, Kanter, Collins, Leonard ...
I mean, my point here is that most of the other really competitive teams in the league have at least a few productive big men with good size filling out their rotation. The Celtics have one -- Horford -- who is somewhat undersized and plays more of a perimeter role now. The only other reliable big man is Baynes, who is solid when he's healthy but has been relatively injury prone in his career.
The Bucks are a team you could look at and say, well, they have size but most of their bigs are perimeter oriented. They're the best or second best team in the league. The thing there is they have a 6'11'' point guard (basically) who grabs double digit rebounds and game and scores at will inside.
The Celts' main scorer is a 6'3'' acrobat who relies heavily on jumpshots. The two man game between Kyrie and Horford is a really nice element to the offense. Horford and Smart work their butts off to make the defense work.
It would all function much more smoothly on both ends if they had some bigs who could set a hard screen, box out, etc. Because it's Brad's offense they need bigs who can also execute handoffs and hit an open mid range jumper, but it's not THAT hard to find guys who can do that.
In fact, there's at least one guy who fits that description who is currently a free agent (Tyler Zeller). Still not sure why the team has never bothered to pick him up.
I'd much rather have Zeller on the team than Yabu.