Hello ApexRon, We understand that CarPlay on your Subaru Crosstrek is unexpectedly loud in Maps but not other apps.
1. 2021 Subaru Crosstrek is not shown as supporting CarPlay: Apple CarPlay - More than 600 models to choose from. - Apple Support
2. Please start by ensuring everything is set up properly as described this help article: Use CarPlay with your iPhone - Apple Support
3. If you still need help, please check this troubleshooting article: How to connect your iPhone, iPad, or iPod touch to your car - Apple Support
There is also a step mentioning the need to check if the car stereo needs an update to work with the new iPhone model or iOS version, stating:
"Make sure that your CarPlay stereo is using the latest firmware from the car manufacturer. Check your car's manual for more information."
Thanks!