Agreed -- these bigs cannot play double big. Only in exceptional circumstances. It should not be a regular thing.
All too slow defensively. Garza struggles to keep up with centers nevermind forwards. Vucevic is a slow center nevermind matching up with forwards. Queta is average in terms of quickness / mobility for a center. He shouldn't be defending quicker forwards. None of them defend the perimeter.
Too stagnant offensively. Not enough movement. Garza is an opportunistic scorer as a center. He is more skilled than most centers. He is not more skilled than most forwards. Nor does his skill-level cause as many problems for forwards unlike centers who want to hang back in the paint and rebound / block shots gifting Garza opportunities he gets fewer of at PF. Vucevic is highly skilled for a center. For a forward, his ball-handling + passing + outside shooting are all below average. The only advantage he has is his physical size and post game. To exploit that well, he needs the paint open. Queta clogs the paint and removes the advantage. Offense gets stagnant trying to create it.
Bad offense. Bad defense.
Double big combination is bad. Plain bad.