WT-11491 improved logging around startup, specifically the checkpoint, log recovery, and RTS stages. But that's not quite enough to diagnose some issues - for example, in the MongoDB test failure linked in the comments, there's a ten-second gap where WiredTiger gives no output and then claims it spent about 2.5 seconds on the stages listed above.

There should be more startup logging throughout wiredtiger_open, possibly as part of the function calls it makes.