I'm firmly in the Maven is better than Gradle camp. Yes, it's less flexible, that's why I like it.

Gradle might be better if it wasn't a poorly documented Groovy/Kotlin DSL where everything is a closure, but I do like the fact that if you want to do something in Maven you need a plugin that couples to known points in the lifecycle. It makes it explicit what is doing what and where.

And fully agree on the incredible pain of Gradle upgrades.

Maven is one of my favorite package managers. It's not as fancy as npm, cargo, go, etc., but it works consistently well and I never have to fight it.