I think the only comment you can make is that, ceteris paribus, newer tech stacks indicate some awareness of newer ideas (who include agile / devops tooling). Old tech might, but also might not.

I'm more inclined to think that Palantir's problems are inherent to the enterprise revenue equation.

"Features and code quality that aren't contractually mandated" = profit

The more things you can put in that category, the more profit...

Newer tech stacks might also indicate chasing the newest/hottest thing without regards to long-term sustainability of the platform, however. You don't always want to be bleeding edge, as bleeding edge can easily be dead five years from now, whereas if you stick with a "boring" mainstream technology it'll still be around in five years.

True. But the enterprise shops I've seen tend to make the "not modern enough" error 20x more often than the "too modern" error.