Maven is well documented and stable tool. Things those can be learned are documented. Most of the plugins are made by maven development team. Maven sets boundaries to stay within - its like standard over all projects.
Gradle has positive side, that is actually also negative side - customization. Freedom to change (add, remove) functionality (re-program, re-configure Gradle behaviour) and boundaries. Therefore, all these changes should be documented - additional work and waste. Usually something are written team members. These changes, differences should be learned by other development team members or sometimes should be checked somewhere (from self written docs or directly from changes in Gradle behaviour), check that maybe something is changed by other team members. Many project, different changes - a deviation from what might be called the standard. Can't be learned once. All that is waste (of time).
Gradle is in Groovy or Kotlin - probably one more language into Java project. Developing gradle scripts. Soon versioning needed. Also publishing to rest of the organization those development enhancements. Gradle development adds more rules on real (business) software developers.
Some cases Gradle projects (modules in development organization/unit) have been tried to make similar in Gradle. Usually ends with hiring a new small team, who makes that Gradle standard component for company. Without hiring that team, the Gradle "standard" management work is put on developers in that organization. To reach good level in that "standard Gradle config/reprogram/extension" takes a time (to analyze, how to do that all "correctly").
At the writing time Gradle (7.6) reached some kind of stability - long time haven't changed something. Until that version constantly something was deprecated. Gradle has some un-stability - most of the time (even with minor version changes) something goes deprecated. Not to mature software.
Usually small Gradle projects have fast build time compared with maven. Bigger Gradle projects have no advantages.
With maven:
- external development team (maven developers) is writing documentation
- some set of maven plugins can be learned once - jumping into any maven project is not so heavy
- stability
Yes, maven can be configured also differently. But still, main line is the same. For example maven unit and integration tests plugins. Usually developers are not learned maven well and doesn't know, that these can be simply separated. Then they start to add some configurations and rules for separation. Then these developers find, Gradle is better, because it can be highly customized. Without learning maven more deeply first!
Why not to push developers to learn these plugins well, so no need to write separate configuration (and maybe documentation) and rules by self? We have maven team who made plugin and documented it already for us.