I think you are being overly pessimistic (while also continuing, like most fans, to not recognize what a replacement level starting pitcher looks like - and Walker was considerably more than that last season). They ran a six-man rotation last year with Sanchez who was supposed to lose his job to Lorenzen, Lorenzen who wasn't any good and Walker who eventually fizzled out. And they still never really lost their iron grip on the position in the standings that they had (with a smaller lead than they have now).
Not cocky or complacent, just realistic. I'm not really in favor of overpaying for a reliever or giving up Miller or Crawford for an OF either. But I'd do either of those things before acquiring a rotation upgrade.
Now, if it's July 31 and Walker stinks and Suarez is on the IL and Turnbull might not seem close, maybe they do something. But it would still just be another Thor or Lorenzen caliber-guy. And they can still get by with Mercado or Phillips or bullpen games, just as they did each of the last two years.
I don't recall them getting any help from their extra starters in the playoffs either year either. They won more in spite of Falter and Thor in 2022 than because of them (even if they did eat innings), and got nothing from Walker or Lorenzen in 2023 (and Sanchez wasn't great either).
If our top 4 pitchers don't 'make it to the playoffs, so be it. You can't trade for a pitcher better than they are out of that fear anymore than you can replace Harper or JT or Turner if they get hurt again.
