That's a lot to process.
Let's try to go line by line.
Yes, they are hard to watch this month. They were also pretty fun to watch out of the gate.
Yes, some of the players I thought could be All-Star material would not be All-Stars if the season ended today. But it doesn't.
I've never said batting average does not matter. I've argued that it should not be the ONLY stat that determined an opinion on a player, because better and more informative stats exist. Don't ignore BA. Don't ignore the others, like OPS either. I can prove that theory. Pick your favorite players, the best hitters in your mind. Check their average. Then check their OPS and even better their adjusted OPS. That allows you to compare their offensive impact to other players across the years. You might be more impressed than you thought.
As for the changes to the lineup, it has not been enough time to make any meaningful conclusions about Dexter at leadoff. If you are going to make switches, you need to give some time for it to click or not.
As for the root cause, that's a great question. Don't know. Good teams play poorly sometimes. Bad teams play well sometimes. I'm not sure the Cardinals can play this poorly for a team that thinks they are as good as this team does. Yes, my big complaint is the rotation. I like that Cabrera is getting a chance to start. It makes sense to test the depth, and move swiftly to add from the outside if a consistent starter does not emerge.