Let's look at those positions' OPS and their National League ranks from start of the 2019 season. That helps us iron out the oddness of the 2020 season without ignoring it entirely, right?
Catcher: .687 OPS, 11th out of 15 NL teams
Shortstop: .743 OPS, 9th
Second: .781 OPS, 4th
Third: .733 OPS, 12th
Three of these positions are critical to that defense-plus identity.
The catcher is a future Hall of Famer and team leader who helps the Cardinals manage pitchers, set defenses, sell tickets, everything, really.
The shortstop is a 27-year-old who was signed to an early contract, has had ups and downs but has presented reasons better is ahead, in addition to improving defensively every season.
The second baseman's offense speaks for itself, though it's rarely viewed in comparison with his position for reasons I don't understand; he's also a Gold Glover.
As for third base? I don't recall there being a shortage of discussion about Carpenter, or his contract. Tommy Edman is a good young player, but I don't think he is The Answer at third base. There is not one at this time, and that could absolutely be a position to upgrade -- if the Cardinals are ready to acknowledge the Carpenter contract extension was a mistake. So far, no signs of that.