Thanks for reaching out on Microsoft Q&A!
It is possible to change an AAD user's password, however this can only be done through delegated access. Please refer to the API reference below:
https://learn.microsoft.com/en-us/graph/api/user-changepassword?view=graph-rest-1.0&tabs=http
When you need help in setting up delegated access, you can find all steps in this great tutorial I've found (and successfully used):
Please click 'Accept answer' if you found it helpful. Feel free to drop additional queries in the comments below!
Kind regards,
Sonny