I
On my one trip to Cozumel, I had more than one experience of the newbie in front of me getting stuck for a few seconds.
There's your problem.
If you very carefully pick the right operator, you won't have a newbie on the boat. On my last couple of trips, I doubt if the least experienced diver on the boats I was on had fewer than a hundred dives. On my last trip, I had days were I doubt if the least experienced diver had fewer than a couple hundred dives.
It makes for an extremely different experience. The DMs take you to places you would otherwise not visit, and nobody has a problem with the swim throughs.