You should be able to install Illustrator version 24.x on your MAC. However, Adobe only supports the latest two versions of the software and only they are provided for download via the CC Desktop app. So the only option to get installer for this version of the s/w is to contact support and ask the installer files from them, they should be able to help you
If you want other prior versions of the software then you can check out the following website, it provides download links directly from Adobe servers so it's perefectly safe. However, the links are not guranteed to work(in case Adobe pulls down the servers providing the downloads), so if you are able to download the software do keep a copy of it.