No it isn't, Creative Cloud provides just two latest versions of the app for download. So that would be CC2020 and CC2019
let's hope the links at ProDesign Tools are still working.
Follow the advice in Note: Very Important Instructions to the dot before you try anything there:
Updates should be available here ( installers for Windows ) :
( Scroll down to see the link for updates for Mac OS X. )
( ACP )
Thanks for reaching out. As mentioned by Manan, only CC2019 and CC2020 are officially available for download through Creative Cloud app. Is there any specific reason you want to download CC2015?
I'd recommend going for the latest version of Adobe InDesign on https://www.adobe.com/products/indesign.html
Hope it helps.